You seriously expect Jack to spend any more time to brood when his life was on the line? That's what would've lead to a dead samurai. He had been at it for 50 years, so he had enough mental fortitude to repress his guilt until he was no longer in danger.
Don't forget he finally broke when he thought all those children died. He wasn't immune to the previous guilt of killing the Daughters of Aku, it merely bubbled underneath for one last straw to break the camel's back.