This is one of the principles I believe, practice and live by.
“Do not always give whatever client wants or ask for but give them something far better than what they never thought they needed. The standards we should set for ourselves have to be higher than those set by client. It is not good enough to produce acceptable work. Nobody pays for mediocrity. Be excellent!”
Being excellent does not mean you do not make mistakes. It does not mean you are already perfect (as a matter of fact no one is perfect!). It does not necessarily mean you are the best of the best in the world (but if you can be that is great!). Being excellent simply means giving of 100% of your best effort into doing something.