My impulsiveness is hurting people

Date: 11/28/2020

I'm sitting outside by the flour mill on the rock wall. Manu and my other friends from Dolores are here and we sit on the rock wall. My friend leans on her bike and plays with her short blonde hair. We become playful and i pick up one of the many rocks on the ground and without thinking, hurl it at her bike. It perfectly hits the tire but bounces up and hits her chin. Obviously she's shocked I'd do that and asks why. I tell her it was impulsive and i didn't think any of it through. I wonder how to express how I'll genuinely never do that again, but it comes up short regardless of my sentiment inside.