Thank you for your answeres so far 
Especially , you wrote some wise words down here. Looking for inspiration instead of looking for motivation is one key i guess.
@Bruno Xavier: I think my lack of motivation is not that i don’t really want to create games. I just have the problem that i have too many ideas. I work on a project for two days and suddenly a new idea comes to my mind which seems a lot better than the old one for that moment and my motivation for my old project is just gone. Maybe i shouldnt worry that much and keep one project going…
@WalkingDead: When my product is finished i have time to worry about that. I also have some marketing experience though.
I wonder if somebody has a concrete story about a project to tell?