Personally, I was rubbish in English at school, until I went on a school exchange in England and met an English girl I fell in love with, which changed my attitude to learning English drastically, but that's another story.
This reminds me of a local garagiste (Dutch by birth) who learnt English at school in France. He too said his English was rubbish (despite being Dutch/French bilingual) until he went to the UK with his then girlfriend, now wife. Her English is apparently better than his and whilst I have never spoken to her in English, it's clear her understanding of me is, at least in part, due to her knowledge of English (if that makes sense)
Off tack a little but I remember a Spanish friend once telling me that she understood my Spanish because she spoke English - that really pulled the rug out from under me! I think she meant she understood my unusual phrasing and, perhaps, inaccurate word choice. Still, talk about demoralising!