Why is Finality Such a Hard Pill to Swallow?

I was having an interesting conversation with my friend when she mentioned how she was struggling with the finality of a certain loss in her life. This got me thinking...

Barring death, divorce, legal impositions/settlements, and other more undeniably "official" examples of finality, why is it that we have such a hard time stomaching irreversible endings? Most of the time, it's not even about the specific person, place, or thing we can't revisit -- it's the entire idea of chapters completely closing without any chance of a rewrite that rattles our hearts. Even when faced with the most resolute of conclusions (with the utmost certainty of closure), at one point or another we have to reckon with that tiny part inside of us that doesn't want to let go.

So, I started mulling over a few possible answers:

• Maybe it's because we fear the feeling of abandonment that often accompanies finality. Sometimes we're just slow to catch up with reality. When we don't expect an ending, it feels like the choo-choo train of life took off without us. No one likes feeling like someone who's one slip of a step behind. 
• Maybe it's because finality imposes on us, over our meekness, as an unwelcome external authority figure...and as a society we're far too used to defying and questioning any form of authority outside of ourselves. 
• Maybe it's because when finality is not what we ordered, we're so offended by our loss of control that we become busy reeling in the aftermath (perhaps even retroactively pretending we actually wanted or meant for it to happen). So busy that we can't seem to sit back and accept that it's over.
• Maybe it's because we don't want to hurt others with our finality. It's so much easier to think "I can't do X anymore" than to actually assert "I won't do this thing with you anymore", "I won't love you anymore", "I won't work here anymore", "I won't be that person to you anymore", etc.
• Maybe it's because we all secretly want to have our cake and eat it too by keeping some doors open...even when we're fully aware that by keeping that door ajar we're potentially losing out on other chances.  
• Maybe it's because we're so great at coming up with alternate endings. We all want to create the Director's Cut version of everything...even after production has clearly wrapped up. It's a shame we'll never really get to direct our own lives -- that's a fantasy that society has effectively perpetuated. (You can, however, leave a fantastically-written memoir in your wake, but I'll go over that option later...)

Well, after all that mulling I still don't really know why and there's only one appropriate way to end this post:

The End.