Adopting a good character, for it is the amalgamation of numerous virtues, such as wisdom, prudence, kindness, humility, foresight, clemency, patience etc. and is thus one of the most important means of attaining felicity in this world and the next. The closest of all people to Allah, the Glorified, and those with the weightiest scales on the day when scales are light, are the ones with the best character. So let each one of you have a good character [in his interaction] with his parents, spouse, children, friends and with all the people. If he discovers some shortcoming in himself, let him not neglect his soul: rather, he should hold it to account and steer it with wisdom towards his goal. If he finds it recalcitrant, he should not lose hope. Instead, he should feign good morals, for indeed, when a person simulates the disposition of a group, he becomes part of it. And such a person will receive greater reward from Allah for his effort than the one who finds it already in his nature [to behave in this way].
(Excerpt of Advise from Ayatullah Sistani)