Need help finding the right thought

I have a job I really like but I’m not doing well. My performance is mediocre. I make a lot of mistakes and have to revise my work several times. My manger is very unsupportive and I feel that she’s waiting for me to leave. I don’t want to feel like I’m incompetent at work because that will only make things worse. I’ve tried to create thoughts like “I’m still learning and I’m trying my best at my job”, or “I’m a great professional who always tries her best.” But these thoughts are not cutting it anymore because I’m starting to believe that I’m just not good at this job. It’s just the reality.

So what’s the thought I can create while I find something else, or if I stick around, to become better at what I do (which I’ve tried to do cant’ seem to be able to accomplish)?