Despite doing more than 4 dozen photoshoots last year, it hasn't gotten any easier for me. Sure, I make less mistakes, and in certain ways, you're more prepared, but the anxieties are no less than last year's. You just know how to better cope with them.
In certain ways, that's good news for me as well. I'm doing something that's not in my comfort zone.
Surprisingly, after a year (or two) of not running my regular laps, I discovered that my endurance was more than it was from two years ago. What used to leave me winded is... less exhausting.
One of the benefits actual running does for me (as opposed to doing the treadmill) is that I run out of breath. There's a certain point where you know your leg and arm muscles can still do the distance, but it's your heart that can't. The reason why people stop running is because breathing becomes more difficult.
There's a right way to jog/run, and proper breathing techniques is one of them. However, it still leaves the runner winded after a certain time. And when you're exhausted, there's a big temptation to simply stop. The benefits of having a regiment or set goal (as opposed to exercising until you're tired) is that you train yourself mentally to stick to it (and of course, not to overextend yourself).
Ultimately, exercise not only trains the body but your mental fortitude as well. Committing one's self to getting up every day to train, and to finish one's regiment, more than anything, is a battle of the will.