Such dumbness is very common with me too, and yet I also call myself a great problem solver, for good reason too.
It's not a paradox, it's a matter if excess focus - once I get into a rut I just keep bulldozing[0], but coming to a problem fresh it's often trivial because the rut hasn't formed.
I'd say it gets better with experience, and you're probably better than you think - my guess is you don't see your successes as clearly as your failures. I guess you spend so much time on the failures, but if you instantly perceive the right approach to a hard problem and solve it in a shot, well, it wasn't a hard problem, right? A kind of bias of perception.
[0]I get the impression that's a bit of a man thing generally
It's not a paradox, it's a matter if excess focus - once I get into a rut I just keep bulldozing[0], but coming to a problem fresh it's often trivial because the rut hasn't formed.
I'd say it gets better with experience, and you're probably better than you think - my guess is you don't see your successes as clearly as your failures. I guess you spend so much time on the failures, but if you instantly perceive the right approach to a hard problem and solve it in a shot, well, it wasn't a hard problem, right? A kind of bias of perception.
[0]I get the impression that's a bit of a man thing generally