That's hard for the 90% to accept. God threw some dice (then He controlled the way they fell) and if your name didn't come up in His book of life, then you're just out of luck. You never did anything wrong. "Nothing" had not even been created yet, and already the Lamb's book of life was fully complete, but your name was excluded. And now God dangles promises in front of your nose about anyone who believes being saved, but you're not so allowed. Your name is not there.
But, it's just as hard to accept for the 10%.
We want to be loved, but in this teaching we are mere lottery winners. God decided to love 10% of x-billion people, and we were just in that 10%. He doesn't love us. He loves .1*x billion humans, and we happened to be born in the right skin.But that's not how He made us.
We cannot be made happy like that.