The answer is that since everything is just OR everything is unjust (you cannot have "some things" just and "some other things" unjust, as I'll be explaining shortly), the word you end up deciding to choose to describe life depends ON WHAT YOU ARE. So, a person who loves life would say that life is just, but a person who hates it would say it is unjust and unfair. In other words, to a strong man life is just; to a weak man life is unjust.
You have a weird way of looking at things.
I like being alive, yet I neither view life as 'just' or 'unjust'. Each experience just is what it is. Why package it all together and slap a fucking label on it calling 'just' or 'unjust'?