[user123456780]

your self reward mechanism changes, as well as the problems youre solving in your 20s are generally new problems to you.

Once you have been coding for 10+, 20+ years you'll come to realise that there is a repeating set of problems you're solving. I haven't seen a truely new problem in a long time. Granted the predominate code I write is for corporate web apps.

But starting out in my 20s everything was new and fun. The reward for solving a thing, or shipping a feature felt great. Now its just one of many features I have shipped that are all more or less the same.

Also another big factor I think is I am significantly more productive now than when I was in my 20s. I would have had to work 80+ hours back then to keep up with myself now