When attempting a MILD, you don’t actually have to fall asleep thinking about LDs. It probably helps, but according to the FAQ on lucidity.com the idea is just to repeat for as long as it takes to ‘set’ your mind with the intention to have a LD.
If you’re dreaming about LDs and having FAs, then you are probably getting pretty close. It’s frustrating to be that close and still fail, but at least it tells that your mind is infested with the idea of LDs, which is always a good thing.
A study was conducted a while ago to determine the easiest way to get to sleep. They told one guy to count sheep, and two others to do different things (Sorry, this was posted here a little while ago by someone else and I can’t remember how it went). Anyway, the guy counting sheep took the longest to fall asleep because counting things (or repeating a phrase) keeps the mind active.
Just do it for 10 minutes, then relax and fall asleep.