STOP mistakes rather than SPOT mistakes

Why do people always keep telling you what you should and should not have done rather than focusing on what you should be doing?

Discussing faults of the past rather than figuring out how to avoid similar situations in the future is a waste of time. Yes, you must learn where you went wrong and how the error could have been avoided but dwelling in the past and never being able to walk out and move on is misuse of time. You keep analysing what happened and now what – arrive at no conclusion at all.
So when people come tell you things about what went wrong, the focus should be on what should be rather than on what should have been!