how to not feel a failure when i don't perform how i want to

i've had long term ptsd related anxiety problems, which affected my self confidence significantly and basically, because of all this, 'fear' has dominated my life for a long time, and because of these real issues, i have times in real life where i struggle to exhibit the qualities i want to show? so for eg- i struggle to assert myself with people....or show self confidence, or take control....and there's times gone by where i've let someone ' tell me' or ' override my will ' rather than me ' tell them'? stand my ground with people......and when that happens, it causes me to self-doubt greatly.......and worry i'm not capable of being the person i want to be?........because fear, bad memories, self doubt grips me, and i can't do it.......can't do what i set out to do.

all i want is to improve my life and overcome my issues to some extent and be the man i envisage? i've been through a lot and showed immense mental strength to get through that, so i do believe it's within me to do it.....but do struggle to display the qualities with people i've mentioned, like i said because of fear and anxiety mainly, so in those times i feel like i have failed? i am aged 48 now.