Why it's easier to spot other people mistake or fault than your own?

Quick answer: lack of information. You can not see yourself with your own eyes.

If there is someone that film you all day, and force you to watch it, you will see your flaw more often.

Why is that? Survival benefit, it's better to see and gather information about the surrounding than info about yourself.

Food, water, shelter, ... all need you to look for them.

So, all things are tied to physics (information is also physics)