Every man should view himself as equally balanced: half good and half evil. Likewise, he should see the entire world as half good and half evil.... With a single good deed he will tip the scales for himself, and for the entire world, to the side of good.
MaimonidesThe whole object of the Prophets and the Sages was to declare that a limit is set to human reason where it must halt.
MaimonidesThe third class of evils comprise those which everyone causes to himself by his own action. This is the largest class, and is far more numerous than the second class. It is especially of these evils that all men complain, - only few men are found that do not sin against themselves by this kind of evil. ...This class of evil originates in man's vices, such as excessive desire for eating, drinking, and love; indulgence in these things in undue measure, or in improper manner, or partaking of bad food. This course brings diseases and afflictions upon the body and soul alike.
Maimonides