Once the season rolls around, a lot of players stop taking the care of themselves that they did in the off-season. The truth is, the rigors of the season, practices, and games require just as much attention as the strength training of the off-season.
1) Drink and eat properly - if you don't fuel yourself right, you won't be at your best. Period. Try filling a car with soda and french fries and see how well it runs. Our bodies need complete foods, not pre-packaged sugar bars and snacks. Eat lots of fruit and vegetables, get some real proteins and healthy lipids (fats, like avocado and fish), and drink tons of water (no, gatorade is not as good as water. It's just sugar water).
2) Sleep - our bodies get to recover when we sleep. It's vital to our functionality, not just as athletes, but as people. Get some good sleep every night. This means planning ahead at times. Don't leave that paper to the last minute or cram for that test. Plan ahead, and get a bit done each night so you never have to compromise your sleep.
3) Lift - you don't need to lift four times a week with heavy sets and high volume like the off-season, but you need to maintain strength. When strength falters, injuries follow. Try to get at least 1-2 lifts per week, with low volume and moderate-high intensity. It shouldn't take more than a half hour to 45 minutes.
4) Recover - there are so many ways you can help your body recover with "active rest" - this includes using the foam roller and manual therapy to help promote blood flow and break up knots. It means doing what we call "developmental" exercises, which address any restrictions you might have in movement patterns. This means perhaps some static stretching in the evenings after practice, and more active mobility work as often as possible.
If you want to compete at the highest level, you need to prepare for it. Take care of yourself the right way, and you will be at your best on the field.