It means to beat yourself down. Here's a list of things fighting yourself is about:
1.Overanalyzing everything you do.
2.Never complimenting yourself.
3.Always downplaying your accomplishments.
4.Comparing yourself to others(and usually saying you aren't good enough).
5.Indecisive about all of your decisions.
The list could go on and on as people tell me I do it to myself a lot so I would know. It's a hard thing to overcome and I try but tend to fail at it. Hopefully OP if you have this problem you are able to overcome it.
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Autism is a disorder not a personality trait!
"God grant me the serenity to accept the things I cannot change,
Courage to change the things I can,
and Wisdom to know the difference."