When you put so much time, effort and energy into a race, you owe it to yourself to think about the race after the fact. And really, unless you never plan to race ever again, this is the most important part of racing: the learning process. No amount of preparation can truly prepare you 100% for race day. Only races can teach you what you need to know to race well.
The best place to start then is to look back on your execution. Did you do what you planned to do? How was your pacing? Did you start too hard then fall apart? How about nutrition, did you ever get hungry? Did you bonk? How about your gear, did you choose the right equipment for race day? What would you do differently next time? Did your competition do anything differently than you did that gave them an advantage? Can you do that next race?
The questions and analysis can be endless. But it is all intentional. No, you're not wallowing in your mistakes, you're learning from them, in the most pointed and acute way. I did a race recently that didn't go so well. Here's how I break that down in my head now:
It was the 2016 Bakers Dozen race. I've done it before a few times so I knew exactly what to expect. But the big X factor this year was the weather. It turned out to be low 40s, windy all day, and just miserably cold. I talked about my teams strategy in my race report on the day (you can find that here), but in short, we tried to do our relay laps shorter than usual to keep from cooling down with long rest periods.
There were two big negatives to this strategy and one positive. On the downside, we were resting 35 minutes at a time, which was just not enough to recover between laps. The hope was it would keep us warmer, but there is no way to stay warm after sitting around for 5 minutes in that weather. The second big down side was that we went harder for the shorter laps, thus burning matches we would have liked to have had later in the day. It's a 13 hour race, so anything you can save for later is huge.
There was a positive side to all of this, however. We managed to open a big lead at the beginning of the race, which gave us a comfortable gap all day. When we started to crash midway through the race, our gap kept us comfortable and the stress low.
Lessons learned: more recovery is better. Especially in cold conditions! Also, I would bring a ton of clothes and blankets to wear in between laps, maybe even a hot drink. Anything to keep me somewhat warm. We burned a lot of energy shivering!
With any post race analysis, it is important to be very honest and real with yourself about your errors on race day. This means that winning sometimes doesn't teach you as much, because your errors don't rise to the surface as quickly, but there is still something to learn there!
Here's another analysis of a race from this (2016) season. I recently got 5th at Iron Mountain in Damascus, VA. Looking back though, I was extremely unprepared. The race report I wrote up for it makes some of those mistakes clear, but my biggest failure was not knowing what the course was going to be like.
Where I live, I don't have access to much technical riding terrain. So when I showed up to Iron Mountain and began riding the most technical trails I've ever raced, I was definitely intimidated. Now this had two opposite effects on me. First, I wasn't stressed out about the terrain that I typically am quite poor at riding, because I had no idea what was ahead. So there is definite value to NOT knowing what you're heading into sometimes, especially when it will psychologically freak you out (same with real life too!). Though, you can't predict when it would be best to not know, so I would say its always better to have a good idea of what the course looks like beforehand than to wing it and hope it helps.
Second, it was a huge negative not knowing the course for prior gear selection. Now, I got lucky with my tire choice. I brought the perfect combination of burl and speed with a Bontrager XR3 up front and a faster XR2 in the rear. But that could have gone very wrong if I had brought faster, thinner, not-friendly-with-rocks tires. My suspension was also set up way too stiff for the types of chunky and rough descents that the course held. I got beat up pretty good on course and at the end of the day, I didn't use about 20% of my front forks travel; that's a painful error (literally!).
However, one thing I did succeed in was noting that the course had one long climb that was mostly gravel. I planned my biggest effort then on that section of the course and managed to distance myself from my competitors, which worked very well in getting me into the top 5. All in all it was a good race, but there are a lot of little details that could have added up to move me the extra 9 minutes up the road to snag 4th place. Next time, I'll be more prepared.
Think hard and honestly about what you could have done to do even better at every race. That might mean getting inside the top 50, top 10, winning your age group or taking the overall win. Regardless of what your next step and goal is, analysis will ultimately make you a much smarter rider for the future.