Good is the enemy of great

One of the greatest lessons I ever learned is "good is the enemy of great".  I first heard this when I read "Good to Great ", by Jim Collins.  By the way if you haven't read this book, I highly recommend it.  It is full of great concepts everyone should know and practice in their lives.  Back to what I was saying, good is the enemy of great.  We must never become comfortable with good.  If we do, we will never become great, and that is why good is the enemy of great.
It is very easy to be good, and to stay good, especially if you are comfortable in that position.  If we do this there is no progress in our journey, and our lives, careers, or whatever it is we are stuck being good at, becomes stagnant.  We must drive ourselves if we are to be great.  We must be assertive.  We must be passionate, and driven to be better than the day before.
If you think you are already great you need to ask yourself, "can I be better", "what can I do to improve", "what am I doing that I should stop doing", etc.  We must never be satisfied with our current position.  We must always be on the move, and always be changing for the better.