Limits, sort of like giving 110%
I really love listening to coaches and athletes talk about a particular performance - "they gave 110% out there today, I'm really proud of them!" or "I knew it was up to me, so I dug deep and came up with 110% effort."
What the heck are they talking about? 100% is all there is, there is no more!
So, how do you know your limits? How do you know you've given 100% of yourself. Very simple, you probably never know, because you probably never have given 100%. I'm not trying to be argumentative or trying to put people down. Endurance sports are tough that way - they take a long time. And the more you do them the more places you find in the effort to give a bit more, to better manage your effort, to get just a bit more out of your body and your performance.
Ignore for a moment the argument that there's improvement with experience. And also ignore for that same moment that age first improves your performance and then diminishes it (I'm on the diminishes it end!).
Think of something you've trained for, for at least 12 months, an event you've done at least three times before (preferably on the same course). Think about your training and preparation. Has it improved over the time you've trained? Have you gotten better at the sport?
Now think about your race performance. Have you learned more about what's needed to improve - like when to push harder, when to relax, how better to handle a segment of the course, how better to handle the conditions - road surface, water conditions, etc.?
So, what is 100%? The best effort you can muster on a given occasion? How many times have you crossed the finish line and realized that, as good as your performance was you knew there was a way to improve? I won a 10 Km race on Fire Island in the 1980s. I was a few minutes ahead of second place. But, in mile one I didn't know where the first turn was, so I had to stop and ask directions (I was already in the lead)! As I crossed the finish line I said to myself, I could have gone faster - if I knew where to make that first turn, I'd have a faster time.
No matter how satisfied you are with your performance, looking for a way to improve it is what being an athlete is all about.