In the morning, you haven't really eaten anything. When you weigh yourself at night, you are weighing all the food and drink you have taken in. Pick one or the other and only weigh in then.
If you are going to win any battle you have to do one thing. You have to make the mind run the body. Never let the body tell the mind what to do. The body will always give up. It is always tired in the morning, noon, and night. But the body is never tired if the mind is not tired.-George W Patton