A line which seems badly drawn rarely is, you just need to understand it. Then you can draw a line in understanding to compliment it. The drawing won't end up as you intended, but the chances are it'll turn out to be a better drawing. The whole thing becomes a bit of an adventure.
It is good to be uncertain and a little lost - in art and life - as long as you remain questioning. In fact, it is more than good... IT'S FUN.