I'm talking about the times where you were trying to find a solution to an obstacle for hours, only to discover you were doing something fundamentally wrong the whole time and it's much easier than you thought. It happens to all of us, even the best of us who think we're beyond it.
Case in point: I was playing Voodoo Vince yesterday, and I got to a section where 3 moving platforms are rotating around in a puddle of water. You die if you fall in the water, so you have to time the jumps so that you hit the platforms as their rotation faces you. I just could not manage to do it, I spent a solid hour getting mad at the game for being seemingly poorly designed, having this extremely difficult section right at the entrance of a new area. It doesn't help that the GameFAQs guide I ended up consulting also stated that the jumps were very difficult, validating and amplifying my frustration.
However, it wasn't hard at all. I had just forgotten that you can stay in the air longer if you do a spin attack after your second jump. Once I remembered that, it was piss easy and I felt like a goddamn moron. That's what happens when you are playing a game on and off for 12 years, I guess.