It is better to have loved and lost
Than never to have loved at all.
- Alfred, Lord Tennyson, In Memoriam

I think the most poignant aspect of this clichéd idea is that when you love, you don't lose at all. So it's not the fear of losing that should drive someone, but it is the fear of not being able to love enough. And I suppose when time is a factor, that's a justified fear. We'll see.