This song was written after Sum 41 learned that a friend of their's got HIV.

"I feel I've come to realize
How fast life can be compromised
Step back to see what's going on
I can't beleive this happened to you
This happened to you"

These 5 lines basically tells you that he was shocked when he found out, because you think it can never happen to you, or someone you know, and then one day, it happens.