That is the best instruction you could ever give a poet: whether you're examining a bad line in a poem or a bad motive for action, keep well your repining - meaning, don't ignore the honest muttering in your head.
To be a poet is as serious, long-term and natural as the effort to be the best human you can be. To express something well is not a question of having a top-class education and understanding poetic forms: rather, it's a question of paying attention.