You have to say "Enough is Enough" to yourself. Go to a room with the least distractions, put your cell phone, electronics, everything thats distracting in another room, far away from your reach and say to yourself I am not going to do anything until I get this done. Hopefully this is enough motivation to help you get started. Once you start, you will be surprised how much you can get done.

Don't open or turn on any internet chat applications either and just make a promise to yourself that you won't talk to anyone until your done.

Trust me, I know what this is like. Sometimes you even have to move yourself to a library or something where it has minimal distractions and should be quieter.

Good luck, and always remember... its not worth loosing silly marks over, just do it and get it over with so you can relax and enjoy your days off or school breaks.

Let us know how it goes!