There's an adage I've heard about grief: look back and be happy about the time you had, rather than regret what might have been.
The Roman lyricists seem to have poems for every possible aspect of love and heartbreak. Are there any that express this particular sentiment? (Greek lyric poetry also works, I'm just focusing on Latin because more of it survives.)
P.S. The most famous English example I can think of is Tennyson: 'tis better to have loved and lost / than never to have loved at all. Something along those lines.