Does suicide end in eternal separation from God?

[tik 🪀✨]

As a post-Christian, I have heard Christians declare to me that suicide is an unforgivable sin. None could ever point at why this was. Perhaps it is the ultimate act of selfishness, ending your own existence. It's playing God with your very being. If you could see me I would be shrugging right now.

[tik 🪀✨]

but what is 'eternal separation from God?'  what makes it so bad?

Because humanity's relationship with God could be its only source of purpose in the universe.  Of course you're a nihilist, so you've given up on the pursuit of meaning or purpose for humanity, but it's a question that troubles me constantly.

Why does humanity need a purpose in the universe? We can fool ourselves with faith into believing whatever suits us to mask the meaninglessness of existence, and therefore be bombarded with complications and implications arising from said faith. What is so wrong with believing that our existence is unexplainable and therefore living our lives simply in the best ways we're aware, seeking no fulfillment besides solutions to that which seems prudent now and in the long term? There is happiness in simplicity and contentedness in simply living to be - for whatever flicker of time we've been granted. Ultimately a search for a "deeper purpose" will arrive to something wholly simplistic, as such.