I think my biggest weakness as a writer is that my reach often exceeds my grasp. On the other hand, it can be a good thing. Provided you actually grab onto something. In that way, I think writing is a lot like aerial acrobatics. There's no net, and sometimes you miss the bar.
I don't outline ("not that there's anything wrong with that") so I often discover obstructions in the road to writing the novel those who outline would altogether avoid. But then, they may miss that little side street that goes down some place you never expected. I think you just have to explore. That's the joy and passion of writing for me. Discovery. It often produces a lot of dead ends, but hey, what are you going to do. Basically this a long winded way of pepping myself up, because I was stuck, and now I'm not.
I was going to bust out a writing as building metaphor (never have too many 'writing as' metaphors) but then I realized if you build something without knowing what it's going to look like, it will probably fall down.