The poet was J. G. Whittier, and he was referring to things that we regret, that we wish we could do over and do differently.
عِبَارَةٌ كَثِيرًا مَا تَتَرَدَّدُ عَلَى أَلْسُنِ ٱلنَّاسِ تَعْبِيرًا عَنْ نَدَمِهِمْ .‏