Besides the general advice on writing (like JSBᾶngs said, "You are not your story" and "Allow your writing to suck"), I think in your case this point is also relevant:

You are not what your former and now very successful peers thought of you/r work: Just because they are very successful now, does not mean that their feedback was right. It surely was not good feedback, because it did not improve your current and future work. Feedback should be specific for the current work and not judge the worth of the person as a writer. They might be successful writers (now), but they did not know how to give good feedback (then), and it should be of no relevance to you. Write for yourself (and your audience), and not for the ghosts of your past, no matter how bright they shine in their current success on a path you haven't taken.

Besides the general advice on writing (like JSBᾶngs said, "You are not your story" and "Allow your writing to suck"), I think in your case this point is also relevant:

You are not what your former and now very successful peers thought of you/r work: Just because they are very successful now, does not mean that their feedback was right. It surely was not good feedback, because it did not improve your current and future work. Feedback should be specific for the current work and not judge the worth of the person as a writer. They might be successful writers (now), but they did not know how to give good feedback (then), and it should be of no relevance to you. Write for yourself (and your audience), and not for the ghosts of your past, no matter how bright they shine in their current success on a path you haven't taken (yet).