Gardenier,
If you are thinking of learning an instrument, I highly recommend the harmonica. It can be carried in a pocket, is a fine accompaniment when you run into another musician no matter what he is playing, and can be played anywhere (you ever see someone bring a guitar into a bar and play it - I do it all the time with my harmonica and is it ever a hit!) Plus, when you are feeling down, nothing beats the harp for blues. It is a whole lot easier to master than a stringed instrument, and you never have to spend time tuning it. And the best part is it won't cost an arm and a leg to buy one, so if you give up and toss it you won't feel nearly as bad.