live to regret something - come to wish that one had not done something:
• Those who put work before their family life often live to regret it
• If you do that, I'm telling you, you will live to regret it.
• If you go down that road, (make that particular decision about something) you will live to regret it.
• Don't do it, you'll wish you had listened to me.
• One day you'll look back and wish you had listened to me.
mark my words - pay attention to what I say
• Mark my words, that man is not to be trusted.
(You) mark my words - something that you say when you tell someone about something that you are certain will happen in the future
• That girl's going to cause trouble, you mark my words.
• Kate, don't go there. Something bad will happen, you mark my words
• Kate, don't go there. Something bad will happen, you will remember my words
• Take note of what I say
• 'bear in mind what I say' (but these two are not as 'ear-catching')
I wasn't sure if I should read the parts in parentheses, so I went ahead and read all of it.