People can't help but feel dumb when they come up with dumb ideas. And that's why most of us are afraid to let go and brainstorm openly.
However, QWT readers know to remain indifferent to the quality of the ideas they dream up. Why? Because you cannot know what an idea will eventually evolve into.
Plenty of ideas seem dumb at first, but aren't. And some ideas may actually be dumb, but they are the first step toward some other idea that could be brilliant. Hey, you never know what might be lurking behind that pathetic idea you just thought up!
Therefore, embrace a childlike, nonjudgmental mental state and just let ideas flow through you--even the dumbest, silliest or most illogical ideas. Lose your attachment to their quality, because at this stage of your creative process the quality of the idea is irrelevant.
Most of your ideas will be dumb. Get over yourself and keep thinking up more. Your ideas may come from you, but they are not--and they never will be--a reflection of your value as a person. They're just ideas, nothing more.
Just because you come up with dumb ideas doesn't mean you are dumb. You are not your ideas.