What did Leo learn from Stargirl?

From the text:

I wonder if I'll ever get another chance. I wonder, but I don't despair. Though I have no family of my own, I do not feel alone. I know that I am being watched. The echo of laughter is the second sunrise I awaken to each day, and at night I feel it is more than starts looking down on me. Last month, one day before my birthday, I received a gift-wrapped package in the mail. It was a porcupine necktie.

Epilogue

Leo thinks back on what he had.... and what he could have had. He learned about the important things in life, though he was too immature to let them sink in. He looks back with regret.