Can not Go Back to Sleep

I suppose to sleep longer but I did not. When I was a teenager I really love to sleep and now that I am still a teenager at heart, I still love to sleep but the problem is, I can not sleep. I slept late and I planning to sleep longer but boy! it's different now than before. Now when someone wake me up that's it, I can not go back to sleep again. Not like before even how noisy it is I sleep like a baby. I just wonder if age is one of the factor lol!