Dave's ESL Cafe's Student Discussion Forums

[jays]

Is "where it counts" in the following correct English? If it is, what does it mean? And does the middle "it" in "where it counts" mean "the mistake"?
---------------- the following ---------------
When I was fourteen years old, I was talking behind someone else's back to a mutual friend. I was being mean-spirited and spreading a bad rumor. I didn't know it, but the person I was bad-mouthing was standing right behind me and heard everything I said. He was upset, and I was embarrassed. This was a mistake I've never forgotten.
This mistake, however, was one of thousands that I made that helped me to become the person I am today. I learned more from that mistake than I could have learned in any class, lecture, or book. It hit me hard where it counts-in my heart. I didn't enjoy it, I'm not proud of it, but I did learn from it. I'm a kinder person today because of it.

[pugachevV]

It's informal English for "Where it was most effective." Or, "Where it did the most good".
It is that mistake .