I don't feel like exercising! I couldn't be bothered preparing the tax return documents. I'm just not keen to study. My question to you is, why should you? The truth is you don't lack motivation. The real problem is not realising that you don't have to have it! There are no couch-police yet. Let's just say it's a choice although feelings can get in the way if that's what you're counting on to get moving.
Feelings rule our world. It's just that we can't always muster up the right feeling at the right time for the desired action. The feeling-hack is simple: take an action first to get your fix of endorphin which will give you the feeling to take another action. American Psychologist Harry Stack Sullivan said it best: 'It is easier to act yourself into a new way of feeling than to feel yourself into a new way of acting.'
In summary, if you lack motivation to do something just start small. Whether it's breaking a large goal into a nano-goal or simply taking the first step only, Do whatever you can to just start the process. In the area of weight loss you might start with 5 couch squats or 5 push-ups a day. If you are studying or learning a new skillset you might use the 'Pomodoro method' developed by Francesco Cirillo where you breakdown work loads to only 25 minutes separated by short breaks. Never underestimate the value of small wins. Sometimes 'go hard or go home' is not the best life philosophy.
Robert M. Hutchins said 'When I feel like exercising I just lie down until the feeling goes away." If you are lucky enough on some days to get an almighty surge - act immediately. On the other days, don't wait for the motivation. Just Nike it, but in kid's size shoes.