Being someone who knows pretty much nothing about making games myself, I find my motivation comes from thinking of the kinds of things I want to have in a game, and then just jumping into Construct and having a think and trying out things until I can get my idea to work.
That's the best thing I've discovered about Construct so far - it allows you to get right in without any real knowledge at all, and in a short time you're able to produce something. Nothing motivates more than the satisfaction of finally doing something or being given something. That's why games like World of Warcraft are so addicting - you're constantly rewarded and made to feel good every step you take in the game.
If you're on a similar level as I am, pick something you want to implement and work it out - you'd be surprised how easy and satisfying that can be.