If you went to the gym and did a really easy workout that was comfortable.. that would be a bad gym session. The goal is to push yourself. Not to injure yourself but to go until failure.
We don't learn in the comfort zone. We learn and grow by pushing ourselves where we feel like we might fail and then pushing until we fail.
Success isn't a game of avoiding failure. Success requires learning and growing from repeated failure. Failure isn't the opposite of success, it's part of it.
Feeling dumb, not knowing where to go, having difficulty even reading and comprehending material is when we know we are engaged in building ourselves.