I doubt it was the "counting" that put you to sleep.
More likely, it was that once you did the counting, you were no longer "thinking" about how many there were to do.
I find that if I have something on my mind or I'm thinking of something I "must" do in the morning, I might as well deal with it, or else, I'll lay awake thinking about it. So when I go to bed, I try to have those things done ... and can go off to sleep.