I really like this quote from Spinoza:
There is no singular thing in Nature which is more useful to man than a man who lives according to the guidance of reason.
Spinoza’s Ethics is full of great little quotes like this. Here’s another:
Hatred is increased through return of hatred, but may be destroyed by love.
This surprising conclusion is based on a couple of premises that Spinoza has put forward previously. According to Spinoza, our fundamental desire is for our own self preservation, because everything that exists strives to persevere in being (this is a claim in physics which is called the conatus – it is false, but that doesn’t affect what follows). Spinoza defines joy as an increase in one’s power of acting, and love as joy accompanied by the idea of an external cause.
So, according to Spinoza, if someone hates us, we can turn his hatred into love by increasing his power of acting. This will cause him to see us as an object of love rather than hatred, and he will love us more intensely than he hated us, because the new love is mixed with the joy of finding that a previous object of hatred is really an object of love.