To your darling, to the light of your life, to someone who is difficult and deeply suspicious of the value of words and the transient nature of feelings, don’t say words. If you feel your heart is full to bursting and you have to do something, just recommend songs. But not in English. Even that would be too much. Try this. This one is called “Caro mio ben” and I’ll link the lyrics below.
I like to (loosely) translate as follows:
Darling dearest, believe this at least —
without you, my heart languishes.
Stop torturing me, cruel one.
My heart languishes without you.