Wrong place at the right time

After class today on my way home, I was at 42nd Grand Central station waiting for the 4 or 5 to take me to bowling green so I could catch the ferry. But I made a mistake when going down the stairs and did not realize I was on the wrong platform. The 5 pulled in and I looked up to see it was the wrong train, out of the corner of my eye I see a sharp movement downward and without thinking I dove and I caught a little kid, about 11 or 12 who has missed the platform and was falling between the train and the gap, I started pulling him up, his mother was helping me and another older gentleman assisted me in getting his legs from between the train and the platform.  the child was screaming in pain, and I checked both his legs, Neither were broken but his knees were badly bruised from the initial drop.I waited with them for a few minutes until MTA personnel came down and when they arrived I went and got on the 4 to go home. As I sat on the ferry I was left thinking How I made a small mistake, my lack of attention to which flight of steps I went down, put me in the wrong place at the right time.