Regret

[Sarah]

When you've done something you wish you hadn't, or hadn't done something you wish you had.

To argue which is worse is an exercise in futility; for the weight of their pain is subjective: the falling out of a friendship because of an unbridled tongue, the loss of the one you love because you didn't speak up, someone committing suicide because of something you'd said. The pain is there, festering; gnawing at your soul; relentlessly reminding you of its reason for existing: yourself. There's no one else you can blame; for there is no one else TO blame. All you can do is bear this burden, because it is a burden you've forced yourself to bear. And you do so willingly- subconsciously seeing it as penance for your sins.

[Sarah]

What you usually feel while waking up with hang-over and a sasquatch by your side.

[Sarah]

Regret is wishing you had said something when you had the chance.

[Hina Muqadas]

A group or gathering of ghosts; attributed to Christopher Moore, author. First Known Use: 2015, First sentence, Chapter 6, Second Hand Souls

[Greta]

Feel sad, repentant, or disappointed over (something that has happened or been done, especially a loss or missed opportunity)

[BertababySog]

sadness associated with some wrong done or some disappointment

[EdwardyHuche]

feel remorse for; feel sorry for; be contrite about

[SanchoPn 0]

decline formally or politely

[Emorynaseaps]

To feel sorry about (any thing).

[ArthuraCig]

Prior has used it in the plural; but, I believe, without authority.

[sastergri]

pain of mind on account of something done or experienced in the past, with a wish that it had been different; a looking back with dissatisfaction or with longing; grief; sorrow; especially, a mourning on account of the loss of some joy, advantage, or satisfaction

[soniportgo]

express with regret