Try going back to some champ you enjoyed previously. I've just played a couple of games as Blitz - whom I played a lot a long time ago then shelved - and both games were excellent, and good fun.
Same for Shen, who was my first main that I picked up again recently. I've been doing very well indeed with him on TT.
EDIT: Just had another excellent game with Blitz. After being behind by 20+ kills, because our Brand dc'd at start, we crawled back once he got back on. He turned out to be an admirable player, and despite being behind by 12 levels initially, he turned out to do very well. Game ended with us winning at 46/46 kills.
Best turn-around ever =)