What does regret mean?

"Well son, the funny thing about regret is,
It's better to regret something you have done,
Than to regret something you haven't done.
And by the way, if you see your mom this weekend,
Be sure and tell her, SATAN, SATAN, SATAN!!!"

- v10 mission statement -

It's better to regret Something you did than something you didn't do.

like Butthole surfers.