I think practice is more important than being right.
I am not a native speaker, I know I am not perfect, and nobody expects me to be perfect, too.
I once told my English teacher that I would feel very embarrassed if I used wrong idioms. She told me not to worry about it at all. Native speakers usally would just feel those mistakes humorous. Come to think about it, it is true that I would never think less of any foreigner who uses a wrong phrase at a wrong situation. I would laugh about it in a pleased way, because most of time I would be amazed that he/she even knows that phrase.
