There are essentially two types of motivation, intrinsic and extrinsic. The intrinsic type is that which comes from within. It is our own reasons for wanting to do something. It is not reliant upon external circumstances.

Extrinsic motivation on the other hand, is provided by forces external to us. The approval of others, financial gain, culture, etc.

While both have a role to play in one's success, the intrinsic motivation is the more important of the two and will buoy our efforts when extrinsic motivation either subsides or evaporates altogether.