This turn of discussion is important, I think. Well done, snoop.

It seems possible that a more positive worldview (whether it includes an afterlife or not) naturally emerges when one begins to let go of emotions/actions based solely on fear. Some fears are rational, but not all...like the fear of death, loss, or pain (imo).

I don't mean to overreach here, but I think these fears are pointless in a sense. Pain might be reasonable to fear, that instinct can save our lives on occasion. But death/loss/afterlife? To me that's likes fearing the sun will rise and set each day and the moon will emerge each night. Why bother? Better to expend efforts elsewhere.

As for why some still grieve?
Because everyone reacts differently to emotional stress I think.
Based on more variables than anyone is willing to read in a single post.

In my personal experience?
Though I have moved on from losses in my life, the momentary grief--that "10 second heartbreak"--never truly disappears. It is there at times despite your most focused efforts, despite all rationality.

Also, some people are more sensitive than others. I for example routinely cry about nonsense things...like commercials, things that happened a decade ago, or things that have absolutely nothing to do with me. Usually with very little warning. Yet many people limit their emotional responses more efficiently.

Emotions are a hotbed of unpredictability, no? Of circumstance and perception and exceptions to the rules and all that lovely grey area that makes it fun to examine and discuss.

I want so badly to know how to answer the OP smartly on this one, but honestly my thoughts on the afterlife (like most things) are so far from determined that assuming a positive outcome is simply out of my league.

Grief can mean many things to many people, though.

Some toast, some bring flowers every year, some burst into tears...
Some just remember and smile.

Even those assuming the best for their departed one are are grieving in a very specific way.