This happens very clearly, because of the “attachment” we develop to people and things in our lives. The attachment to people and things, over time, becomes so overwhelmingly, strong, that it makes you dependent. So dependent on these people and things you have become that the loss of them renders you heart-broken and helpless.
Practice detachment
What if, instead we choose to be detached from all people and things? Detachment is, not the renouncing of all people and things and living the life of a hermit. But it is about living a really full life of fascination with all things and paradoxically attached (dependent) on none of it. Because it is only when you grow attached and dependent on things are you going to miss their or its absence. This way, even as someone departs from this physical existence, there is no bereavement.