Sometimes, it can be hard to keep a good outlook on life. Bad days happen, and sometimes, it can feel downright impossible to smile when your hair looks scary on the night of your big date, your dog died, or you got in a fight with your best friend. Sometimes it's all you can do to not hide from the world... (I would have had an image here of my husband's cat, hiding under blankets, but I couldn't get it to load)
I've been told I've got a really good outlook on life. Most are surprised when they find out I've had depression because apparently I'm "always sunny."
Part of keeping a good attitude, in my humble opinion, is making yourself crawl out from under that blanket and do things. From the writers' perspective, bad days can be especially knarly. When I feel down, I have a hard time writing. Words evade me, and I find myself picking out flaws in my work (regardless of if they're true flaws at all). But I sit down at that computer anyway and try to put down something, and it helps. Often, all it takes is one decently crafted sentence to brighten my day -- silly and simple as it is.
When I'm with friends who feel cruddy, I drag them out somewhere with a "c'mon lets go get ice cream," or a "Let's go take a walk" or "Let's go check out that exhibit at the museum." Doing things, no matter how small, helps get your mind of the bad stuff. The main thing to remember is that life doesn't stop on a bad day -- life keeps rolling.
Make the choice to roll with it, because, tomorrow is a clean slate. :)