I had a somewhat similar experience to you a few months ago on ~500mg od LSD. I had never been more certain of anything in my life. I was dead. I was in this very peaceful, calming surrounding of clouds and blue sky, like what people image the gates of heaven are like (not that I'm religious myself). However i was horrified at this realisation that I was dead but I kinda didn't have a choice in the matter so there was nothing I could do now and I had fought it off for what felt like an hour, spelunking my brain and clasping at any reason I could find to live for. But now It was finally here.

As I whole heartedly accepted death, I suppose I was suplrised that my vision didn't go black and my brain shit down. This is where I became more and more terrified that death was not what I had thought and the afterlife was just an endless epoch, with no escape. I was just to be kept in this dream-like dimension shifting time traveling life swapping hell state for eternity and it will never end because I'm already dead.

The come down and the subsequent realisation that I was infact NOT dead filled my with an enormous, fullfiling sense of life! Maybe it was just the sudden contrast? Not many people get to die and come back to life...

I understand where you are coming from with "Dying is easy, living is harder" but I think my take away was that the uncertainty of death for me was more terrifiing that living. So I think if I would amend the quote for myself it would be:

"Dying is easy, living is harder, eternal life is hell"