when i start to feel like that, i just read something, not something of magic, and i watch some movies, and play some games, like 2 days, i take a time from magic, and then, i look for magic performances, good ones, the performances that i like, in my case Penn and Teller, The virts, D&D, and DG, this ones cheer me up
.
then i start to re-reading my magic books (chapters i like), then watching some of my dvds, and then i just start thinking why i start into magic, i remember why and i remember my performances, the reactions of my spectators, and so, and that cheer me up a lot. and then i just spend 9-10 or even more months like crazy/hyper/kid practicing, performing, watching, creating, and more.
This is my way, and maybe for you is different, and you may need to find ur own way to cheer you up.
peace.
* another think i do is draw/design gaffs/backs/etc that help me, and even that makes me create some new effects/routines (even they r just thoughts, this help me).