It's human nature to overestimate.
When it comes to exercise and nutrition, we like to think we've burned more calories exercising, or eaten fewer calories, than we have in reality.
Partly because it's so hard to track either of these accurately, and like I said... it's human nature.
The 300 calorie run burned 400 calories, the 500 calorie meal was only 400.
It might make you feel better, like you're on track or you've got room left in the tank, but your results will suffer.
A trick that I've carried with me for a few years now, is to purposely underestimate.
If google tells you your run burned 400 calories, take it as 300. If you estimate a meal to be 500 calories, take it as 400.
If you're wrong and you have actually underestimated, you're left on the positive side of progress.
This "go one more" type mentality can carry into everything that you do.
Take it that one step further, and reap the rewards of exceptional results.