'Tis not a silly question, this is perfectly respectable.

Everything mentioned so far is good, especially exercise which works wonders, but if that/diet/friends are not an issue, then my guess is that perhaps there is something deeper down that you feel is missing from your life, or maybe things are not going in the direction or speed that you would like them to.
I guess what I'm trying to say is, instead of trying to find a 'quick fix' for your spirits, take a moment to comtemplate the source of the trouble, and try to work from there.
My two cents, anyway.
I take drives at night
I do this as well when I feel down. And as cheesy as it sounds I find taking a hike through natural wilderness (assuming it is accessible) is great for the spirits.
