This is the same 6500-word essay linked in the OP. It might be helpful to note that (I think) the relevant part is the very last two paragraphs. And you say there that you are not sure what Becker meant by practicing dying. The concrete method you describe is:
I’ll lay down in bed and imagine that I’m about to die in the next 5-15 minutes. … When I first started doing this I found it very distressing, but over time I’ve gotten a lot more capable at soberly considering the end of my existence.
https://www.thelastrationalist.com/memento-mori-said-the-confessor.html
This is the same 6500-word essay linked in the OP. It might be helpful to note that (I think) the relevant part is the very last two paragraphs. And you say there that you are not sure what Becker meant by practicing dying. The concrete method you describe is:
Ok, I imagined it. I shrug.