People face motivational deficits because they are going against the way or doing something they don't fully agree to. Hence, part of them is not cooperating.
Every iota of your being knows the way, just like it knows all the chemistry involved in your body. You don't have to run your body, yet it keeps running. This intelligence is what rebels when you do something wrong. You face an instinctive lack of motivation when you are called to lie, cheat, and deceive. If you ever feel unmotivated to do something, it may be against the way of the Universe or outrightly immoral. Your body is cognizant of the right principles because it is the Universe. And it follows/presents/executes them [the right principles] by making you flinch. You still have free will, so you can violate your body and go against the flow. But this violation will not stop. You will someday have to depend on some sort of drug like alcohol, porn, and religion to avoid sensing your painfully rebelling body. It's a downward spiral. This is why immoral people are highly prone to addiction. The more drugs you take, the more addicted you will get. Life will only become more and more painful, until one day your conscience and spirit (I don't know how else to say this. I wanted to say chi) start to leave. This is spiritual death or decay. Thus, those who live in sin are dead. Then, these spiritually deal people cause immense harm to others. They become agents of evil.
Perhaps, a part of you is not cooperating because it flows in a direction that the rest of you does not. Motivational gurus will tell you to enslave your body and make it do what your ego wants. This way, you only become a slave to your ego. You become egotistical and proud. Your body is the universe. And the universe does not like to be controlled. Control antagonizes [this word is borrowed from an Alan Watts' lecture) it. The right way to deal with this to give up trying to control the part that is rebelling and allow it for once to lead you to places it seeks to take you. Perhaps, it's a blind spot, where the mystery lies. When you allow all parts of you to grow and mature, a sort of metaphysical integration starts to emerge. The more you give up control, the lesser the split (feeling that a part of you is going astray) gets. Eventually, you reach a point where you no longer feel that split. The spirit has healed itself. At the same time, you may have to give up your ego and your plans to allow yourself to be redirected to something much grander (some call it calling), where you rightfully belong. Therefore, don't try to rule over, but don't be a puppet either. Engage in a relationship with the unknown, a sort in which sometimes you lead and sometimes you allow being led. To know more about this, try this and this.
Don't follow new-age motivational gurus. Don't flatter your ego by torturing your body. Take a step back to think if you are controlling things you shouldn't. If you have a problem, there is something you are holding on to. And you need to let it go. You must unbecome. Allow things to unfold and watch things get done. Allow the unknown to carry you to your destination without your trying to control it. Trust me. It roots for you whenever you give up control and play alongside it.