Avoiding stimulants, like caffeine, energy drinks,
monster drinks, nictoine, etc. is obviously a biggie too. I know, easier said than done...but cutting down on these things really does help. (I say that to you after two cups of coffee and a smoke...lol...so know I'm not indicating that this stuff is a cake walk).
Sleep...to improve your quantity and quality of sleep is very helpful.
Diet..a healthy, well balanced diet does wonders for the psyche.