Just adding to what Namu said, if you procrastinate, take all your distractions away from you- even for just 1 hour.
I had my parents take away my Tv's and computer's power cord, remove the wii and playstation, my PSP and DS out of my room for about 1hour for starters. Then i increased this time slowly by 30min increments and slowly everything began to reappear in my room. It sounds a bit stupid- but it works and i can actually do work in my room now without being so distracted
And don't worry shiftyness, i didn't study for my SC either but i used my prelims to form great study habits. Don't stress too much about your prelims because they're just that- your prelims, but rather use it to learn great habits for year 12- if you push yourself too hard in year 11 you'll burn out