When you're in the middle of a stressful situation (e.g. studying for finals) you can use these tips to feel better.
-Take a break from what you're working on and do something you enjoy- a hobby, watch TV, just sitting, etc. Leaving the stress behind even if it's just for a little bit will make you feel a whole lot better.
-Get some exercise! Research shows that exercise is a great stress reliever. You don't have to go to the gym- just do some jumping jacks or run in place for some quick and easy exercise or make it fun and play a group sport.
-Get a good night's sleep. Staying up all night and studying isn't going to pay off in the end most likely. A decent sleep will let your body and mind rest, so you can be ready to conquer whatever tasks you need to do during the next day. Not getting enough sleep is just going to engender more stress.
-Laugh! Can't get much simpler than that.
-Deep breathing exercises and relaxation. You can look these up online if you're interested.
Hope these help!