what motivates me is getting things accomplished.
for example, i used to be just like you, so i get what you mean, it sucks big time...but don't fret.
make a to-do list, prioritize.
do the most important stuff first. it is a fear, a fear of attacking things that must be done. if you don't think it's a fear, you're still in denial. you are afraid of doing your homework or studying, because you think it's boring and you're afraid it will be a boring-ass waste of time.
you worry, you make excuses to do less important stuff.
real motivation comes from getting stuff done and from success. you have to build momentum.
success breeds success.
the most difficult thing is to get started. once you get started, i'll warn you...you may not be able to stop. it's just that damn motivating to get stuff done.
and start your to-do lists early. it's not like i'm extroirdinarily proficient yet, but for studies, for example...
...i write down the dates of my tests/projects/deadlines for each class, the upcoming ones. then i write under each, the work that needs to be accomplished to prepare for that deadline. i paste those lists on my wall in checklists. that's it. as long as i get those things done by the deadlines, my life is easy as pie and i can just do anything else in my free time. and damn it feels good to check stuff off the list. sometimes i challenge myself to see how many things i can check off in a day.
i guarantee you, once you start you can't stop. and i don't mean that to be a cliche or rip-off of a chips motto...it's so true, success breeds success.
you just need to start.
good luck, and just do it!
btw, i also wrote a more coherent tip a while ago that covers a similar topic, as i tackled with this a few weeks ago before finally learning some actual time-management:
http://www.sosuave.net/forum/showthread.php?s=&threadid=84929
(read Chapter II)