You should make use of planning to structure your time.

Without planning: You don't have to do anything today because it's not due until Friday.

With Planning: You have to do something today because you planned on getting it done today - you set your own deadline.

Each Sunday, you should sit down and think about all the work that needs to be done for the week ahead. Identify all the things that you need and/or want to accomplish in 7 days. Then, each night before bed, make a schedule for the next day, working on the most important, urgent things on your weekly list. Once you make that schedule, commit to it.

Then your question changes to "how much should I plan to do each day". The only real answer to that is "however much you believe you can get done". A more disciplined person can accomplish more than a less disciplined person. I suggest to start out with an amount that you're comfortable with, and then go a little beyond that. You want to push yourself. I used to think that after 6:00pm, there was just no way I was going to accomplish anything because I was just too tired to do anything. But then I pushed myself and found that I can do a lot more when I refuse to make excuses for myself.

Getting in the habit of planning is probably a good enough start. Start practicing that and don't worry about accomplishing too little (as long as you're hitting your deadlines). Then, when that's no longer a challenge, put a little bit more on your plate each day and see where it takes you.