If you don't travel now, you might 'live to regret it'. [=you might feel sorry or disappointed about it in the future]
We 'regret' to inform you [=we are sorry to tell you] that we have offered the job to someone else.
It is to be 'regretted' [=it is regrettable/unfortunate] that the program has lost its funding.
(..) I don't know half of you haIf as well as I should like... ...and I like less than half of you half as well as you deserve. I have things to do. I've put this off far too long. I regret to announce this is the end! I'm going now. I bid you all a very fond farewell. Goodbye. (..)2001 The Lord of the Rings: The Fellowship of the Ring