Jinn, I've been doing the exact same thing you're talking about for all of my academic life... and seeing as I'm in my 3rd year of grad school, that's a looooooooong-established pattern for me!
Seriously, I don't know what's wrong with people like us. I don't go around promising my boyfriend that I won't masturbate or drink caffeine (why did you do that, by the way?), but I am not very self-disciplined in all the ways that I imagined myself being, as a grown-up. This depresses me, often. At the age of 26 I'd hoped to shake these things off, but jesus, sometimes I wonder if I should really be in this field at all. I don't function well without structure, and I'm very bad about imposing it on myself... the latter is crucial to success in grad school.
So my advice to you is to scrape your way through college, and find yourself a nice, structured job where you are given specific tasks and deadlines every day. If I was smart, maybe I'd do the same... hmm.