Lament

la-ment (l-mnt)
verb
1. To regret, sorrowfully.
2. To express such regret and sorrow.
Although she was smiling on the outside, she inwardly lamented the events of that morning. If she hadn't mentioned the cheese, he probably wouldn't have got so angry and it wouldn't have turned into such a heated argument, but there was nothing she could do about it now.
He lamented the loss of his friend so loudly and so often that the whole neighborhood knew about it.

Synonyms: bawl; bemoan; complain; moan; pule; regret; sulk; whine.

noun
1. A tangible or intangible expression of regret and sorrow. Tangibly, these usually take some sort of rhyming form, like a song or a lengthy poem. Intangibly, it might be like that invisible burden one carries with them everywhere they go, so that it effects their posture and eventually bending their back until they look like a lamentable old character.

Gone was the joy
behind her eyes.
All her smiles
turned into lies.
She regretted
everything.
Each breath, a sad
song she would sing.

John Lennon's lament: "Although I laugh and I act like a clown. Beneath this mask I am wearing a frown."

Synonyms: dirge; emo poetry or really any kind of emo art at all; requiem; the song "Loser," by the Beatles or any song by that name by any band should qualify as a lament; sorrow.