Motivation is a feeling that leads to action. It feels like desire, but it's more specific. It's a desire to do something or to be someone. Motivation is a useful feeling because it can help you push through difficulties. Even if you can't act on your motivation or you don't have many difficulties, feeling motivation can make you feel more alive and present. It makes you feel good. If you can learn how to isolate the feeling of motivation, then you can learn to recall it when you want to feel better, such as when you don't feel like doing anything or when you feel sad.
One way to recall the feeling of motivation, which I've learned from Headspace, is to meditate the question, "What is your dream goal?" and see how your mind and body reacts. When I meditate the question, I feel the motivation in my mind and chest. I can feel my mind light up, like it's waking up, and I can feel air rushing into my chest. I recognize this feeling as motivation, and I can often recall this feeling without the question to help me accomplish what I want in that moment.