Celebrate his life. And maybe read some other things about the many much more healthy perspectives cultures around the world have developed around death.
Sadness is fine, that's part of processing a loss. But neither this loss nor the appropriate sadness are terrible things.
Also, I don't believe it's said that Men join Eru in death. Just that they will take part in the music after Dagor Dagorath. I think you're sweeping numerous other mythological influences under the rug if you choose to view that as predominantly Abrahamic in origin.
It brings to mind how Iain M. Banks wrote in the Culture series about beings who chose functional immortality by uploading their consciousness to networked hardware. One of them still programmed himself to need to pee in the simulation, because he liked doing it.
Whereas I'd be surprised if any being programmed themselves to die in the simulation and be wiped away.
But if they did, I'd love to know their reasoning.
I do not remember the books go too much into details about the reason for this tradition though.
Basically an avoidance of the kind of entrenched dogmas Eric Weinstein has been podcasting about.