Focus on the homework only, sometimes we can be distracted by many things, including music, computer phone. Its surprising just how many things can stop us from staying focused. Remove your self from all distractions, sounds tough I know but its better than having it hang the burden of guilt over you for hours.
I agree with murenti, you have to focus on just your HMWK. also, dont try to plow through everything at once, take regular breaks. also, do the hardest first, then when you are flying through your easy HMWK, you will be like, "hey, this is easy!" Also it is kind of funny that you mention concentrating on HMWK... I am suposed to be doing my homework right now... LOL