Who is to be blamed when expectations are not met, yourself or the one who failed to do it?

Depends ,did you set the bar to high
assuming someone else would reach their potential
and not yours
We are not all the same
You have you're gifts and talents ,I have mine
They should compliment each other
Not yours cancel mine out

In my experience, it's usually the fault of the other person, because I never expect anything from anyone until they make a promise to do something. It's entirely on them if they fail to deliver.

the one who failed, but not because they failed. They didn't set realistic expectations.

Me. I shouldn’t have expected to be of any importance to anyone. Tf was I thinking. 🙄

How can someone else read your mind?

Depends on the history between you and the individual.

Many times, there is "blame" to found on both sides of that.

The person whose expectations are too high.

I would be the one to blame as I expected too much.

The expectations setter.

Depends