Victor, I'm 76 and have been building software for 50 years. I can no longer put in 12-hours a day for 6 days a week for 3-months at a time. Fortunately, with my knowledge, experience, and patience, I no longer have to.

Never underestimate the value that is gained from 50 years of mistakes (evaluated and fixed). It is a priceless learning experience if you put in the effort to learn from it.