Don't, we're all idiots with these things at some point in life.
James Oliver Rigney, Jr. was a man who obviously loved his writing. He invested a lot of his time into this series. And while it does suck that he will not see his work come to fruition, he will have lived his last days doing what he loved. Think about it, his last few days were spent doing something that mattered to him instead of sitting in fear of death. In fact, he actually can be quoted as saying:
"I’ll keep on writing until they nail down my coffin." - Robert Jordan
His passing away is sad, but whenever you will pick up a WoT book, you will be sharing in his passion for that work. And when "A Memory of Light" comes out, this book will be his final gift to his loyal readers.
Yes, death sucks, but you should appreciate what he has given you instead of regret what he hasn't been able to do. (This is pretty much how I've seen death for quite some time.)