Well, it sounds to me like you do. I was in the exact same boat not too long ago. It might be hard, but what you need to do is decide that you will only start things that you will definitely finish. Start small, maybe with something like a short jog. Tell yourself before you do it, “I am going to jog for exactly one mile.” Then do it. Don’t go over, don’t go below. Do exactly what you set out to do, whatever it is. Just keep the goals small and realistic at first and then eventually you can move that habit of finishing things into work and school. I hope this helps. Medication might also help, it helped me quite a lot.