Hi butterfly :}
the other people said so many great things, the topic of 'failure' is near and dear to my heart so I dont really have advice.. just some "mental images" to offer that may help, that have helped me.
like so many here my parents were excessively demanding perfectioninsts. they taught us nothing, but expected us to know everything. my way to deal with this was to become a devotee of 'failure' in all its spectacular, messy glory. i became an artist. in the world of art, there is no right and wrong. there is only what is there. its up to *you* to name it or categorize it as success or failure. its a metaphor for life to me.
my very best work was often created from what others would have called 'mistakes'. i found that those 'mistakes' were really a gateway to the most creative and unprecedented thought. one of my best drawings was one that was partially destroyed by a dog ripping it up. i just used the ripped parts as part of the design, and it turned out way more interesting than it was before. every person that paid me money for that poster thought i meant it to be that way.
when i would sell painted tshirts, sometimes there would be spots or smudges for different reasons. instead of selling those shirts for less becuase they were 'flawed', instead I painted butterflies (yes butterflies

and other beautiful things over the smudges, so that each smudge became instead a beautiful extra thing, and those shirts became my most popular and sold for much more than the ones 'without mistakes'.
our 'failures' or 'successes' are up to us to decide.
some quotes:
"people fall down - winners get up"
"Ideas do not have to be correct in order to be good; its only necessary that, if they do fail, they do so in an interesting way." - Robert Rosen
I also think about the fact that it took Thomas Edison more than 100 tries before successfully inventing a working light bulb... It took women almost 100 years to get the vote. It took almost 100 years to invent the birth control pilll. Anything that was ever invented that we take for granted now, was often the product of a loooooong process of 'mistakes', failures, and roadblocks during which some poor soul refused to take no for an answer. Many things that we use all the time were actually mistakes BEFORE they were invented, that people then thought, 'hey this is cool' and started to use. I see this all the time in things even like cooking. you dont have oregano, you use basil instead. then it becomes your favorite recipe. all becuase of a 'mistake'.
none of this is really advice... its just mental images on the concept of redefining 'failure' and 'success' for ones self. life is a process.. not a perfect, shrink-wrapped destination as we were taught. cutting off our access to the potential of 'failure' is just another way to stifle our creativity, our life force, our unique way of being who we are and contributing to the world. dont you let them do it!!
as far as reprogramming our thoughts, i agree with some others that its not magic, for me its been simply discipline. ive seen the power of negative programming.. so, why not use a little positive programming. it has made a lot of changes in my thoughts, with time, patience, humor, and a LOT of forgiveness of my 'slips'. it still hurts to have other people critisice you. im not discounting that. those tapes in the head are powerful. just offering a different point of view.
just a little musings on 'success' and 'failure', from someone who has taken failing 'to an art form' :}}>