Loss
From the perspective of the experienced eye, I guess you could say that having something to loose means you care so deeply for something that it has instilled a fear in you. A fear so strong it has changed your ways, and fabricated a whole new you that you never expected to exist. And this loss can come from all walks of life. Perhaps you'll begin to observe the most miniscule of things in your efforts to take in the beauty of the world, before your breath escapes for the last time. Maybe your every waking moment will be to revel in his laughter as it reverberates through and around you. As fear holds potential truth to the fact that that might as well have been the last time you see his green eyes disappear behind eyelids crinkled in laughter, or the last time that this sun will ever shine on your face. A luxury denied by very many.
So I guess my answer is that loss creates fear, but not fear of living, fear of living without.
And if loss has already happened, then, hopefully, you have memories that resonate for the rest of your lifetime.