This works. Happiness depends on your outlook and it often comes to whether you want to be happy or not. This is of course over-simplified and doesn't apply to everyone for whatever reason, but I thought it shows that happiness does require effort on your part if it's going to be a part of your outlook.
What do you think? Are you happy? If not, change something. Help someone with their shopping, start jogging regularly, get a new book to read, sit in the sun everyday, drink more water, write a book, begin a diary, eat better, join a sporting team, get a massage, or make a blog. Plenty of things to change if you feel like a little happiness-perk. Just in time for summer too. Get happy!