Humans may or may not have cosmic significance and if they do it will be by hitching a ride on the objective centrality of knowledge in the cosmic scheme of things.
I did a lot of things that I regretted and I certainly paid for my mistakes. You have to go and ask for forgiveness and it wasn't until I really started doing good and doing right by other people as well as myself that I really started to feel that guilt go away. So I don't have a problem going to sleep at night.