It's too easy to blame other people in life for things that we're responsible for. You could blame the marketing producers for making the food look so good that you're overweight. You could blame the US for the bombings in other countries. You could blame your doctor for not telling you that you had cancer earlier on (even though you hadn't been to see him for five years).

I have a massive maths assignment due on Tuesday. I haven't done it yet. I can't complete it because I don't have my maths book at home with me.
I could say that "I didn't know until a few days into the holidays", but that would be abstaining from responsibility. I should've checked.
I've been trying to get the maths book of other people in my class. I could say that I don't have a maths book for me because other people are being slack in getting it to me, but that would also be abstaining from responsibility. I should've tried harder to get a maths book.

I'm royally fucked because I'm a lazy prick. Don't let the same happen to you. If you need to do something, do it now so you can enjoy the rest of your day.

edit: Its not what you know, its who you know. Especially if who you know happens to be able to help you with your maths. Got it all done :)