How do you work, study, read, etc. even if you don't feel like it?

I took four cles. I was messing around until spring break. Then I pulled myself together. During that break, I studied 7 hours a day for a week! Around 50 hours of studying. I got 3 "B's" and 1 "A" on my midterms. After that point though, I have not studied a single day! It has been nearly a month and I have not touched any book!That week was my most productive ever! But, it was also one of the most miserable days I have had, because at the end of the day sure I had a lot of work done... but my day was completely gone. I was tired, and wanted to have fun.Now, I cannot seem to be able to force myself to stu