Perception is a funny, funny thing. I know this, but I forget it, until something reminds me.
Last Monday, my weight felt normal. Tuesday, I felt as if I'd gained weight. Wednesday, I felt as if I'd lost weight.
My weight hadn't changed at all, but my pants fit differently and that altered my perception of myself. My perception wasn't reality.
We can go through this as writers as well. We think we're great, we think we're awful, we don't have much of an opinion. Just as my sense of my own weight had no connection to reality, so can our sense of ourselves as writers be an illusion.
Perception isn't reality.