I have a hard time thinking to myself 'i can do it'

Im trying to work on and improve myself. But one problem i have is i struggle with saying 'i can do it'

Im constantly tripping myself up or saying to myself 'just give up your not gonna get it right'

I need to think 'i can do it' so i can stop failing and actually try to improve my life, but im having such a difficult time thinking im actually good enough to say 'i can do it' and not back down or talk down to myself

How can i change this?