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.
(..) ...and have a job. What do you really want to know? Am I sorry for what I did? Well, are you? There's not a day goes by I don't feel regret. Not because I'm in here or because you think I should. I look back on the way I was then... ...a young... ...stupid kid who committed (..)1994 The Shawshank Redemption