Some days are better than others, and on those bad days we can have a tough time thinking rationally. While there are ways to beat a bad day, when you feel bad you can often feel like a completely different person. If you just can't shake those bad feelings, treat it as an opportunity. Study your behaviour, keep track of what helps you out, and write it all down in a personal handbook that you can reference in the future.
Photo remixed from an original by Paul Downey
Consider a bad day from the past and the problems that came up. Motivation was probably an issue. Did sleep help? Did you feel better after eating something? Perhaps the solution was more unique than that. If you're unmotivated to work, consider it an opportunity to do something else and take note of the effects. It may do nothing at all, but eventually you'll come across an answer. When you do, make a note in your handbook so next time you feel that way, you can look up possible solutions and give them a try.
Your handbook can be a physical notebook or a digital one, but the important thing is how you make the entries. You don't want to list solutions under a header of "bad day" because that's generic and pretty much encompasses everything. Instead, try to describe how you feel. Use descriptions that you'll understand. They do no need to make sense to anyone else. "Unmotivated and lethargic" may be how you'd communicate how you feel to someone else, but "unmotivated, don't even want to feel better, chest discomfort, and sugar cravings" is an example of a more descriptive and personally accurate set of symptoms.
Putting together the handbook is going to take some time and effort, but when you're not feeling good it will give you something easy to do. Sometimes the worst thing about having a bad day is that it seems to just get worse since you can't motivate yourself to do anything. Chances are you can motivate yourself to eat, sleep, listen to music, play a game, watch TV, or do one of the many things that could shift you into a better state of mind. If you don't succeed, then you've learned something about what works with that particular situation. With a little work and some patience, you'll eventually have an entire personal handbook full of answers to all your problems.