For example, I think the taxes are too high:
1. I can complain all the time, and be miserable.
2. I can work to change it - but lets say it takes me 10 hours a week to make any dent at all, and I'll only save 10k -- not worth it.
3. I can wish that it was lower, but do nothing and just live my life as it is. Though, I may feel anger or frustration - negatively impacting my life.
or lastly
4. I can change my position - I guess the taxes are good, I get this stuff that I need, etc. Now I'm happy with my current situation and don't have any need to change it. By changing my perspective I've removed a source of pain in my life, even though it still exists -- I am no longer consciously aware of it.
A little bit more on the concept of slave morality, it applies to Nietzsche's critique of Christianity:
"By saying humility is voluntary, slave morality avoids admitting that their humility was in the beginning forced upon them by a master. Biblical principles of turning the other cheek, humility, charity, and pity are the result of universalizing the plight of the slave onto all humankind, and thus enslaving the masters as well." [1]
He argues that in early Christianity instead of glorifying standing up to their oppressors, which was difficult and fraught with danger, that they glorified being subservient - when the master hits you turn the other cheek, don't defend yourself