Writing grad school letters - TME/TMA ..please?lol

as the title says; was curious about hearing people's' experiences in the past with such. Have you ever written a letter and included something you were iffy about only to NOT hear back from the school thinking it might have been that? Or the opposite, what have you included/how did you word something that really made you stand out? I'm good at writing letters but need some reaffirmation since this is so important - I think I'm being too self-critical.

But anyways, thanks you gays!