One way or another, expectations are everything. This is one of those realizations that I've had over and over again in the last ten or fifteen years, so at this point I'm convinced it applies to pretty much everything. A few examples:
Dating. I think the most unhappy daters I know are people who approach every first date hoping the person will be the love of their life and/or match a mile-long checklist of criteria (looks, job, education, financial, religious, fashion, sense of humor, personal habits, feelings towards pets / kids, etc. etc. etc.). The happiest (and most successful) daters I know are people who approach every date as nothing more than a chance to meet someone new and have a good time for a few hours. Because their expectations are a little lower (I mean, not abysmally low), they usually end up having a better experience.
Teaching. In my years as a high school teacher, one thing I have definitely learned is that kids will live up to your expectations one way or another. If you expect them to work hard and learn, they will. If you expect them to give up and quit, they'll do that too. I've also seen students' attitude and motivation toward a task change when I've discussed with them ahead of time what they can expect to experience emotionally (good at first as they get started, a bit of self-doubt as they get stuck, a desire to give up when they're not sure what to do next, a feeling of accomplishment and pride when they push through their discomfort and complete the task).
Adversity. It's amazing to me how the way I (and others) react to the exact same situation can vary so dramatically based on what I'm expecting. When I've known weeks or months ahead of time that I'm going to have to endure something unpleasant (ie, a stretch of very long work days, an unpleasant meeting, or an annoying travel situation), I usually only feel mildly irritated but generally manage to stay pretty positive. When the same situation is sprung on me suddenly, it's occasionally made me into something of a monster.
At a certain point, I realized that the same is true of distance running. In a previous post, I described the shock and helplessness I experienced the first time I really, truly ran all-out at a cross country meet. I can only describe that feeling as complete and utter despair; I simply could not believe it was possible to hurt so much in so many different ways and, even worse, that that was what was supposed to happen and I was honesty expected to deal with it in some way. Looking back, I'm actually sort of shocked that I finished the race and didn't just collapse on the course in a shuddering, sobbing mess.
But the second time, it wasn't quite so bad, even though I ran just as hard. That is, it was just as bad, and that's exactly my point. Somehow the familiarity of all that pain and exhaustion and the desperate desire to quit running no matter how I had to rationalize it was exactly what I needed to get me through it. I started to anticipate that last "killer quarter" (the last 25% of any race where you absolutely just want to die) and see it as my nemesis, one who never gave up trying to get the better of me but who I'd narrowly bested enough times to know that I was the stronger of the two of us. "Ah, you again," I would sigh inwardly. "Well, if you insist. Let's see what you've got." This eventually progressed to a kind of pre-race pep-talk where I'd find myself in the days and hours leading up to a race telling myself things like, "You're going for a fight. Don't even think about holding back. Beat the shit out of this thing." This was the start of the Loop of Audacity that has gotten me through some very dark places in terms of running over the years.
I experienced something similar when I first started training in San Francisco. I have this loop in Golden Gate Park that I run pretty frequently, anywhere from seven to 15 miles depending on how you do it; the first half is slightly downhill on average, and the second half is more than slightly uphill. The first few times I ran this loop, I would inevitably run the first half at a pretty good clip with minimal effort. "What a GREAT run I'm having today!" I would find myself thinking. Then I'd hit the turnaround and head back the other way. Almost immediately, there's a noticeable and rather longish uphill, and inevitably, not five minutes into the return trip, my legs would feel leaden, I'd feel myself breathing harder, and it would seem unthinkable to me that I could only be halfway. "Ugh, this run SUCKS," I would think, plodding my way up the hill at a glacial pace. Towards the end of the loop, there are several similar-looking turns, and especially on longer runs, I would tend to forget which one I was on and feel a rush of defeat each time I realized that the corner I'd just turned was not the last. That, my friend, was not a lot of fun.
I don't know how long it took me to see the pattern (too long, I imagine), but one day before I started out on that run, I found myself thinking the entire route, remembering not only what every piece of it was like, but what sort of self-talk each part inspired and how it made me feel, and why. I took the first half a little slower, careful to avoid the trap of running gleefully fast in the first half of a long run, and as I neared the turnaround, I found myself thinking ahead to the long, winding uphill I was about to confront. Let me be clear, that didn't make it any less physically unpleasant, but it did make it much easier on me emotionally. I still had that exhausted, leaden feeling, but because I had thought about it ahead of time and remembered that it was coming, I was able to stay more positive and probably plodded up that hill slightly faster than usual.
Developing accurate and reasonable expectations has made a huge difference in my running and how I experience it. I've also found it tremendously helpful in helping out new runners, similar to the way I've found that it helps my math students to be given a road map ahead of time about how they can expect to feel at different points in working through a hard problem. It really helps beginning runners to be told ahead of time about the emotions and self-talk they can expect at different points in a hard race, or while running up a hill, or doing intervals for the first time, etc. When you know what's coming, your brain has time (consciously or not) to prepare for how it will respond and react and get you through the tough parts (as opposed to the hopeless flailing I experienced in my first race).
Managing your own expectations can be useful in less cerebral ways as well. These days, I find it enormously helpful to conduct a "premortem" before a hard run or race. I first encountered the term premortem in the work of Guy Kawasaki (Enchantment: The Art of Changing Hearts, Minds, and Actions), who works with entrepreneurs. Organizations routinely conduct a postmortem after completing a big project, in which they reflect on what went well, what did not go well, what the causes were, and how the whole process could be improved. In a premortem, you think about the project you are about to undertake and imagine it failed, think about all the possible reasons why it could have failed, then try to figure out what you could have done differently to change the outcome.
In "premortem-ing" a big race, I first try to imagine every possible way that my race could go badly or not as I've planned (I get hurt, the weather is hot / nasty / windy, I go out too fast, I oversleep, I forget a key piece of gear, I go the wrong way, there's some problem with my Garmin, etc.). Then I make sure that I have a plan for how to avoid that problem or how to deal with it the best I can in the case of things I can't control (like the weather). It's through premortem-ing that I've developed some good habits & routines for preventing certain problems; eg, at this point I always take the time to put on every piece of gear I'll need the night before, then take it back off and either lay it out or put it in my bag. This helps me avoid forgetting things.
Even on shorter runs, it's helpful to remind myself what physical and mental challenges lie where. It reminds my brain and body that I'm expecting them, and that I've got tools for dealing with them and not letting them take control of my race or run. Somehow, this makes tough things a little easier to handle psychologically.