For example, I often think I am unusually cowardly or clumsy. Then I am totally surprised when I find after like 3 months of martial arts practice I am already better on both accounts than like 20-30% of the new starters, I was sure I will never ever get better at it, which roughly predicts average ability - but then why does it feel so unusually low?

I tend to think others are far more social than me. Then I start wondering, the fact that we are living in the same flat for 3 years now and never had a chat with a neighbor cannot be 100% my fault, it is 50% mine for not initiating such a conversation, but also 50% theirs as they too didn't. So it may actually be they are not that much more social than me.