My Son is a Quitter...and I Respect and Appreciate That

My son has never been Mr. Outgoing. He's not the one who'll jump straight into the fray in and amongst strangers just looking for a good time. He and I are introverts and he's quite a cautious one. This is who he is and I both respect and appreciate that.
He's done soccer twice now. This last soccer season, he started off not going on the field during practice or games without me holding his hand. That's what he needed, that's what he got. By the end of the season, he was on the field by himself, running around like a maniac (still dodging the ball when it came to him, but he was dodging it all by himself!). He grew and he enjoyed doing it. I respect and appreciate that.
During that time, he blossomed socially. He made friends. He even took "buddy pictures" with his friend Bella, so he can remember her always. He spends at least a couple days a week with his coach's daughter and new favorite chum, Georgia. He's still my cautious introvert, but he's a changing cautious introvert. Most importantly, he's changing of his own accord and at his own pace. I respect and appreciate that.
Yesterday, he went to his first basketball practice. He got his own ball with his name on it, his own 80s-style sweatbands (so rad!), pumped himself up with his jams on the way there, and was the first one to arrive. He was stoked. He even got me to be the assistant coach. (Poor kids!) Unfortunately, basketballs are hard and noses are bustable. Mid-practice he got a ball passed to the middle of his face, which resulted in a bloody nose and a little shiner. "Basketball hurts" according to him. I can't argue. He doesn't want to do it anymore. It's his body and his life. I respect and appreciate that.
After several talks, he decided he'd rather do soccer again. Yes, there's something to be said for learning not to quit when things get hard, but that's a lesson we're teaching through modeling and without creating miserable experiences that will sour him for life. He's four. He has plenty of time to try any number of sports, activities, and hobbies...or not. It's up to him. Maybe he'll try basketball again later. Maybe he won't. Maybe he'll play soccer for years to come. Maybe he won't. Maybe he'll do another sport or not. Maybe he'll spend every afternoon reading in the hammock in the backyard. Maybe he'll do ballet or gymnastics or krav maga, maybe he'll really dig the Baden-Powell Service Association that he's starting this fall and he'll stick with that, maybe he'll want voice lessons and spend his weekends doing karaoke on the Wii. I don't care what he does or doesn't do as long as he does what makes him happy as opposed to what he thinks will make me happy. I respect and appreciate him.