Always bite the bullet. Often you will know that a piece of code should be refactored or needs better tests; or tests at all. It's always tempting to not fix

Always bite the bullet. Often you will know that a piece of code should be refactored or needs better tests; or tests at all. It's always tempting to not fix stuff or rewrite as you go because this isn't the core of what you've been asked to do. If instead of taking the "easy" option you are constantly making the code better and simpler you will by definition be a better programmer.