External motivation matters. Who doesn’t want a really comfortable place to live? (As I write this morning, the repairmen are working on the AC). Or the approval of those we love? Still, the inner drives are potentially strongest. I work hard because I feel good about myself when I do. We’re wired to do what feels good. Joy and self-worth are just higher needs than the physical.
So what makes you feel good about yourself? What gives you a sense of accomplishment? Where’s your joy? I’m not advocating blind leaps of life change, but the things that make you feel proud of yourself are the things you can usually find the energy to do. Do them!
If you want to read more, the psych terms are extrinsic and intrinsic motivation. Also, Abraham Maslow had great insight with his hierarchy of needs. Explanations are widely available; I referred to the wiki entry awhile ago when writing to my nephew.