Something doesn't have to be permanent to be good. Something can be ephemeral and be good too. And it doesn't have to come via edict from a deity. It's just that I define those things in a way which is different than a Christian would. Shorn of the underlying logic, I believe something is good if it is kind, evil if it is cruel.
All ethical systems begin with at least one axiom.
Happiness is good in its own right. So, the general ethical goal I try to accomplish is to increase the amount of happiness and decrease the amount of unhappiness in the universe. To me, that's a worthy goal irrespective of whether it has any other result. Everything I believe in ethics derives from this. I cannot prove to you that happiness is a worthwhile goal.