Motivation to have motivation?

Is it normal I can't understand how motivation actually works? I know this is a recurrent topic but I'm looking for more in depth answers. I know there must be a reason why some people are able to motivate themselves to accomplish their objectives, I just can't figure out what that reason may be.

Right at the beginning of Philip K. Dick's novel "Do Androids Dream of Electric Sheep?", in a scene which was not in the movie, Deckard has a conversation with his wife, Iran. It's 3 to 4 pages long so I'll sum it up and go straight to the point that makes me think of motivation and the inability or lack of desire to achieve it. The couple talk about the moods that can be dialed on the Penfield Mood Organ - a device that, roughly speaking, allows users to choose their moods. Despite that, a melancholic Iran does not wish to leave her state of depression.

"I don't feel like dialing anything at all now," Iran said.
"Then dial 3," he said.
"I can't dial a setting that stimulates my cerebral cortex into wanting to dial! If I don't want to dial, I don't want to dial that most of all, because then I will want to dial, and wanting to dial is right now the most alien drive I can imagine; I just want to sit here on the bed and stare at the floor."

The thing is, I can understand that well. What I really would like is to learn about the desire to leave such states, the feeling of wanting to do the things you want to do - if that makes any sense, because it seems contradictory that one would have desires and intentions but not be able to materialize them (excepting of course concrete impossibilities, such a financial situation, physical disability, etc.) and if you are a person who is able to keep yourself motivated, what drives you?