I think the main thing that has made me feel happier is just having 'Me' time!
Spend some time doing something you really enjoy, or if its a really bad day, just make sure you take care of yourself and get some rest, and try again the next day.
Like I really love reading sometimes, and just getting comfy in my bed on my laptop, singing along to karaoke's or instrumentals on youtube, playing the Sims 2 or going on Facebook and being nosey

Haha *()
Sometimes being with your friends can help too, because you can get away from being inside all day, and just try your best to have a laugh and get away from it all.
Doing exercise or going to the Gym can help a lot too, not only is it good for you but it makes you feel good about yourself because you've pushed yourself to do something good with your time :) It's just doing it thats the problem! I've been trying to get out of a lazy mind set recently!
So I guess just do something you enjoy, but make sure you've got a good balance on having fun and you're 'priorities' like work or cleaning the house etc, a fair share of both is pretty good

Take care everyone! xx