When days are bad and you’re feeling really down...force yourself to whistle or sing a happy tune. Find a song that you like very much and which is catchy and fun, memorize it and whenever you need to give yourself a lift, just whistle or sing it.
Try some midi music:
http://notendur.centrum.is/~sih/midi/
There are also many happy children’s songs that might do the trick for you, so find one of those:
http://bussongs.com/animal_songs.php
