Go to bookstore and find a good book or magazine, get a massage, take a walk, go to toy store with my kids (its fun for all of us), have my husband cook dinner and enjoy a beer while he bbq's (instant de-stress). I love going to see a kids movie with my daughter.
Planning something to look forward to is the best thing to beat the blues. I get stuck in a rut in my life often because it seems most of it is repetitive and on autopilot, then one day I wake up and I'm feeling a bit bored and bummed...so that's when I do something I enjoy no matter what matters are pressing at home or work (I work from home and stay home with kids so I'm on double duty...all the time). If I need an escape and I'm with my kids alone at home...I jump in the shower and ease my stress- they leave me alone in the shower.
Sometimes I wallow in my mood and let it be. We are programmed to always be happy (by society's standards) and that's not necessary- to know happiness one must know sadness.