If you are really upset or sorry about something, you might lament it. A lament is full of regret and grief.
If you lament something, then you feel sorry about it. You could lament a mistake you made, or you could lament a horrible thing that happened to a friend. Also, a lament is an expression of grief. So if you keep saying how sorry you are about something, someone could say, "Enough of your laments!" There's also an old literary form called "a lament," which expresses feelings of loss in a long dramatic poem.