That’s a very powerful lesson with insights into the motivation behind people who put you down. They have problems which they are failing to deal with. Such problems may include jealousy, incompetence or simple childishness.
It can even be related to deeper problems in their life, which they are not addressing in the right manner.
When you realize this fact, you will have conquered much ground to maintain your self esteem, dignity and personal values in the face of put downs.
And more importantly, you will be able to separate factual comments from insults or careless statements meant to put you down. If it is a statement of fact, you obviously need to evaluate it with the respect it deserves.
But if it is not, you should straight away know that you are dealing with a unreasonable person who has no respect for their own dignity, let alone yours. You should understand that their attempt to hide from their problem involves trying to humiliate you or make you look and feel less important than they are.