Well first off, Jiu-Jitsu is very young and didn’t have world-wide exposure until after UFC 1. To put this into perspective, many of the first generation Black Belts who started training BEFORE the UFC are just now reaching middle age:
So, ‘mistakes’ are a bit of a misnomer because I don’t know that Jiu-Jitsu has reached a critical mass of experience to draw yet from? Hard to say. =)
The above being said, here are some things I would have done different:
1) Prioritized health and wellness and been more mindful of my body.
2) Paid more attention to defending strikes relative to positioning.
3) Relaxed more.
4) Listened to myself instead of assuming some people had ‘the’ answers, assuming they were somewhere ‘out there.’
5) Strived to understand principles instead of copying positions wholesale.
6) Rooted my game more in defense and survival, and less on guard and guard passing for a more complete, flowing game.
7) Had more fun and took myself and Jiu-Jitsu less serious.
8) Less sparring, more thoughtful drilling and refining.
9) More awareness of who I surrounded myself with and their respective worldview(s).
10) Have a more balanced life, with interests and friendships outside Jiu-Jitsu.
In fairness, just reaching the tipping point of middle age myself and these are things I’m in the process of correcting now. Good fun. =)