A genuine love of what you are doing. Someone who practices something purely because they want to be good at it will never reach the heights of those who do it because they love it.
It is my nature to give my best no matter what the task at hand may be. That is not a point of pride, as it can be a weakness or a strength depending on the circumstance.
Positive encouragement from others working with me to achieve the desired result.
If I enjoy it. The only things I excel at are things that I like doing, otherwise I'm pretty lazy and just can't be bothered. I am good at cooking and sewing and I think I could do those all day and be happy :o)
Excelling IS the motivation