While people may treat you rudely (translate, “I don’t like you”) or dismissively (translate, “I don’t respect you”), you must do everything you can to maintain your dignity and self-respect.
Tell yourself : “others’ may not perceive my talents, but I know that I am a great person.” There have been times when I have actually said to myself “my mother loves me, ha.” I would say this to keep myself from getting discouraged. This is an exercise that you can do easily, and you must do this exercise every time that someone has treated you badly. Tell yourself the opposite of whatever perceived insult you have endured.
People may treat you poorly, but that is no reason to feel worthless or have low self esteem. Human beings are fantastic creatures with resilience and great capacities for love. If you need it, point the love to yourself.