Quotes on exchanging glances and (therefore) imagining a relationship

Hi there,

I've spend the last hour or so trying to find out in which movie I heard a quote. And I can't figure out. I don't have the exact thing but the (male) character says that what's great with (exchanging) glances is that you can imagine what the (love) relationship with the person would be without being confronted with its failure.

I'm not sure if the character think that every love relationships are doomed, but maybe.

Maybe it's not from a movie and I'm totally confused.
I thought in the beginning that was from "When Harry Met Sally", but doesn't seem so...

Many thanks!