Motivation means we have an idea and we are going to carry through on that idea. We work hard at it, and we are disciplined. A highly motivated person takes an idea, goes out there, and won't let anybody interfere with them.
Inspiration is exactly the opposite. If motivation is when you get hold of an idea and carry it through to its conclusion, inspiration is the reverse. An idea gets hold of you and carries you where you are intended to go.
-from Dr. Wayne Dyer's website.