I studied that we can't depend on our motivation

Today I was disappointed one thing about project I've joined. My motivation of this jobs lost. But I can't stop and run away from this project because I'm in charge of one part that is closing of this project.

What I want to say, if we lose our motivation, we are disappointed a thing, or we think we don't want to work and run away, the jobs chase us. So I studied that we can't depend on our motivation. We don't beleive it because we are the emotional animal. 

I think that if we don't have no motivation about any jobs, it's not problem and we should finish our jobs we face now.