If you have no regrets, you fall into one of two categories:
- You didn't try
- You didn't pay attention
That's it. The technical mistakes you regret are just part of the learning process. This is the time in your life to make those mistakes. The stakes almost could not be lower. Yes, these competitions mean a lot to you, as they should. But the regret you may feel now will fade with time. These are small regrets. Don't sweat them.
Failing here will not cost you your job, your living, your home, or your ability to provide for your family. The coin in which you pay now is pride and prestige, and maybe a couple of trips out of town. What you learn now will make you less likely to derail or damage your career in the future.
The regrets you truly want to avoid are the interpersonal ones. Be ready to make mistakes in technical contexts, expect it to happen, even welcome it. You should be much more careful in how you treat your teammates, your opponents, your mentors and coaches, and how you represent your team and your community. (The few mistakes I've made there are the only ones I would go back and change.)
Of the fantastically talented engineers I've known, there's a few that I think little of as people. (One or two names, you would recognize.) Given the choice between working or socializing with them, or with lesser engineers who are outstanding people, I'll take the latter every day and twice on Sunday. The work will still get done well, and it will be a lot more gratifying.
What would you rather say? We won Worlds but I hated the experience and half the people? Or that we fell short on the field, but I loved everything we did and everyone around me?