Motivation

what makes a person motivated?

One question that always comes to my mind everyday and I still can't find the best answer. Can you?

It comes to me that to be motivated you need to find something or someone that will keep you focus in aiming whatever your goal is. What if that someone or something left you, what will become of you then?

They say to stay motivated you have to love what you do. Then, what if you are starting to fall out of love? what is the next thing to do?

Motivation?

as per google and general term - is a reason or reasons for acting or behaving in a particular way. 

So, how can we stay motivated then? what is the best way to motivate ourselves especially when we can't find anything special in what we do anymore?