The physical (and genetic) demands of athletics aside, we were talking about writing. Just starting on a lark is what worked for Haruki Murakami. Again, it's very unlikely you'll be the next Murakami. But at least you'll improve a lot at something you find interesting! What is the downside here, exactly? Unless you're an opportunity-cost-minimising, industrial-output-maximising kind of person. That's fine, but that's not everyone.