One of my favorite "feel better" tactics I take is a relaxing afternoon/evening to watch kids movies. Yes, I'm only 19, but a lot of people I know stopped watching them when they were about 10 to 12 years old. I like to still watch them.
Right now, I'm watching "Happily N'Ever After 2" (I haven't seen it so I have no idea if its good or not) though my favorites are classic Disney movies. It's a nice little escape back to a simpler time.
So next time you aren't feeling so great, pop in some "children's" movies and grab some popcorn.