I don’t think you are talking about motivation so much as work habits. Many… maybe even most people put off doing things until it is too late to do them, and then they rush through doing a half-assed job, but getting by anyway.
Some people are more disciplined. You can become more disciplined by creating a schedule for yourself. You can plan what to do when. You can divide the semester up into blocks of time, and see how little you have, which generally gets you going.
I always tried to do the reading in time for class. I was able to do that probably 90% of the time. Sometimes I skimmed the material, but it was enough. I almost never got a C, and I probably had as many As as Bs, if not more.
Papers are the hardest thing. That’s because you really do have to plan. You need to set aside time for research and time for drafting, and time for editing. You also need to build in time for thinking, or talking about it with other people.
So I would suggest you identify all the work products you have to create for each course, and then figure out what you have to do when in order to create those products. Pin the schedule on the inside of your eyelids (or wherever you cannot fail to see it all the time), and check things off as they are done.
Oh yeah. Include time for friends and entertainment and parties and boys in your schedule. I generally did that stuff on weekends. I would suggest you resist week day partying. It really messes up your schedule.
I never had to do this on paper, but then I have always been able to keep a project plan in my head and know where I am in the process. It’s instinctive, I guess. Although, nowadays, I do put certain projects down on paper—but that’s when I’m trying to do more than I can actually do in that amount of time. It helps a lot, but I always seem to end up leaving out a couple of things at then end. Doesn’t matter. People seem to love it anyway. I’m the only one who knows what didn’t happen.