What does Mr Tushman think the true measure of someone’s growth is?

From the text:

"But the best way to measure how much you've grown isn't by inches or the number of laps you can now run around the track, or even your grade point average—though those things are important, to be sure. It's what you've done with your time, how you've chosen to spend your days, and whom you have touched this year. That, to me, is the greatest measure of success."