I play online video games or go on a walk outside There are many things that make me feel better, but walking around town is definitely one of the best.
Only you know what will truly make you happy. Some people it's getting outside on their own, some people it's learning something new, some people it's getting out and socializing. For me I love to go bush walking with my dog and go fish some of the local streams it's away from civilization and it's relaxing.
smoke a few bowls of weed, play some games, watch some movies, download and listen to random audiobooks and mp3, do any or all of the above at the same time.
personally, i used to skate when i was stressed. exercise and the personal satisfaction of landing a sick fliptrick ive been working on is pretty rewarding.