How do I not be overwhelmed?

I need some support. some comfort. Last month when I spoke with somebody I realized that it's my parents constant belittling me from when I was young that I get overwhelmed quickly now, because even though their words were lies and I never believed it how "You're a failure" "You're never going to succeed" etc. All these I knew were wrong, but as an adult, still lies, but I get overwhelmed because internally something in me feels "What if I fail" or "I'm not sure I can do it" even though, I know I can do it, but there's a thing inside that.. feels otherwise x.x. You know what I mean? Does anyone have any words of wisdom that might help me break this? Please let me know