I feel dumb the entire time I'm looking at a level, and then when I beat it I have a brief instant of imagining I am so brilliant that others must surely shrink away in shame, and then I realize I'm stuck on a new puzzle and Qtian and my friend and his mother and her dog are three puzzles ahead of me.
I think most people tend to feel this way when faced with difficult tasks. Same thing happens in my programming job. Some tasks are just really challenging and force you to think. I find a lot of programmers (especially beginners) wind up feeling dumb because of this. I definitely used to, and our current new starter feels like this too.
But there's no need. You cant get everything right away, some things really do require a lot of thought. Try to learn to enjoy that process of discovery, rather than fretting that not knowing makes you dumb. It doesn't. The discovery part can be just as fun when you stop thinking like this.