Take enough sleep, and besides this, I think it has something to do with your diet. I didn't eat anything in at least 1 hour after the workouts, and I found I'm terriblely hungry and tired until and eat something. I finally fount that I should avoid keeping an empty stomach no matter it's before or after workouts, or you'll get tired and your muscle will be resolved into blood glucose, mineral substance and animo acid if you're hungry, so more harm than good. Intake some calories and protein both before and after exercise.