(principle of) letting sleeping dogs lie; peace-at-any-price; don't rock the boat
better be the head of a dog than the tail of a lion; better be first in a village than second at Rome; (lit.) better to be the mouth of a chicken than the rear end of a cow
do not do unto others what you would not have done unto you
do not befriend those beneath you
do not delay in making amends for your wrongs