I have my garden flowers on my screen saver at home.  So whenever I'm sitting there wondering what to write next or taking a short break--next thing you know...my garden drifts across my screen and puts me in a good mood.  Now, granted, everyone's not a flower person.  But in the event you are, I welcome you to my garden.  For non-flower lovers, you can look at the photos as colorful meditation or as a brief escape from earnest or weighty thoughts. 
Although I eat a lot of chocolate too.
There's no point in relying on just one thing to make me feel good.