"Bye, my darling."
Translation:Tìoraidh m' eudail.
I would (and do) address using "mo ghràidh" for "my beloved" and "mo ghaol" for "my love", but that's just from what I've picked up. They could both be well off the mark for proper usage.
I think "gaol" is a bit stronger of a sentiment than "gràdh":
"Tha gaol agam ort" - I love you
Compared with the sentiment here (I'll include the entire first verse because, well, it's just lovely):
Eilean Fraoich, Eilean Fraoich Eilean Fraoch nam beann àrd Far an d' fhuair mi m' àrach òg Eilean Leòdhais mo ghràidh
Final line - "my beloved Isle of Lewis". Emotional, wistful, strong, but just feels a tad different from calling someone "my love".