I don't think that's it. My lucid dreaming can happen when I have slept, been awoken by something and then turn back to sleep. It can too happen if I have slept too long. I never tell myself anything before. Using cellphones before make no difference. If you perhaps not pressure yourself it will happen, when you kind of don't care if you lucid dream or not? I think it is about a different kind of relaxment? You will get there