State of mind and amount of thinking definitely affects your ability to enter dreams: dont think enough and you'll succumb to the dream or dreamlike state unaware. Think too much and you wont be able to fall asleep at all.
It's hard to find an exact optimal solution, and I'm sure it's different for everybody. Try to experiment.

Also, entering dreams first time you hit the bed is not easy. In fact it's one of the most difficult things to do, otherwise just about everybody would be doing that....