rue the day (that something happened)
To curse or bitterly regret a point in time (in which something happened or one did something). I swear to you now, you will rue the day you ever crossed me! Men, if their soldiers advance upon us, we must ensure that they will rue the day!
rue the day (that) (something) happened
To feel bitter regret or remorse that something has happened; to wish that something never came to pass. That no-good, lying cheat! I'll make sure he rues the day he crossed me, if it's the last thing I do! Your dad must be rueing the day he agreed to buy you a car if you got an A in all your classes.