What are some thoughts or ways to counter this?

Hello, I went through decades of that.
I even called it my self destruct mechanism.
Every time it looked like I might get ahead in life I would tell myself exactly that, "Who do you think you are, get back in the gutter where you belong and do not attempt to better yourself again"
That is exactly what I would.
Do something to sabotage whatever it was that gave me an inkling that I am deserved of advancement.
For decades I remained in the gutter, head down, not speaking up for myself.
One day I had had enough.
The next time those negative thoughts entered my head I would very forcefully, out loud say, "Get out of my head, you are not wanted"
I would repeat this several times, after a few weeks, those negative thoughts started to decrease in frequency.
Now days, those negative thoughts do not enter my head because I learned that I have as much right as the next person to be valued and accepted in this cutthroat world.

You need a cheerleader in your life. Someone who will make you feel worthy. Who will motivate you and cause you to want to do better and be better. Everyone needs someone in their corner. We can be hard on ourselves but when other people see our potential we stop and take notice.

Realise you were brain washed into thinking like that... And once you start thinking like that you cute everything through a negative lens... And so you don't try... You give up before starting...