Definition:
Regretful- Sorrowful and apologetic; wistful.


Example:
“Halfway through shaving, it came- the word for a poem. I should have scribbled it On the mirror with a soapy finger, Or shouted it to my wife in the kitchen, Or muttered it to myself till it ran In my head like a tune. But now it’s gone….”
“Gone Forever,” by Barriss Mills


Explanation:
The author is wishing that he had done something to remember the word, but he hadn’t, saying what he “should have” done. He cannot do anything about it now. He is also sorrowful that he didn’t.