How to manage our own motivation

A human is unique. He / She sometimes has very good and strong motivation to do something, try to think more, do what is in his / her mind and keep it alive. But in another chance he she forgets what is in his / her schedules, or may not do anything .
So when we have down motivation to do an activity it is better for us to control our mind by always be ready to read or listen to something good and positive in order to make our selves motivation keep strong and energetics.