Why do narcissists use their new partner to make their ex look bad, and what's really going on behind the scenes with this tactic?

Why do I tend to be inattentive about subjects not of high interest to me, like the learning curriculum?
What are some reasons atheists might have a lower incarceration rate, and how does that challenge common perceptions about morality and religion?
If I die, nothing will change right? After, everyone has to move on like nothing bad happens in the future, right?
Is it true that getting older automatically means you'll be in constant pain, or can you stay pain-free with the right lifestyle choices?