Lately, when I have trouble falling asleep, I imagine Bing Crosby singing "Count Your Blessings" from "White Christmas."
http://www.youtube.com/watch?v=DXKxazgio2s
I've also heard Rosemary Clooney sing it, so sometimes I imagine that. Or, for variety, I think of the Pied Pipers singing "Dream (When You're Feeling Blue)."
http://www.youtube.com/watch?v=ZLLEc-Xh068