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.
(..) Chris, I fat-shamed you, and I believe I owe you a weaselly political apology. So, if you took offense to anything I said, I certainly regret that you did that. At this point, I consider the matter closed. Thank you so much, Principal Shepherd. I know that was very difficult for you. (..)2020 TvShow: Family Guy Title: Movin' In (Principal Shepherd's Song) Season: 18 Episode 20