The key to power, then, is ...

The key to power, then, is the ability to judge who is best able to further your interests in all situations. Keep friends for friendship, but work with the skilled and competent.
 Robert Greene

Quotes from the same author

Your ability to work with people directly affects your ability to get work done in the world.
 Robert Greene
You have the power to think differently about who you are. You have the ability to turn off the critical voice inside of you. That's not you. That's coming from the culture. That's coming from the outside of you. You've internalized the voice of your parents, your teachers, your friends.
 Robert Greene
All the most successful people nowadays who are truly successful and innovative in their field are not people motivated by money.
 Robert Greene
Our levels of desire, patience, persistence, and confidence end up playing a much larger role in success than sheer reasoning powers. Feel motivated and energized, we can overcome almost anything. Feeling bored and restless, our minds shut off and we become increasingly passive.
 Robert Greene
Understand: people will constantly attack you in life. One of their main weapons will be to instill in you doubts about yourself – your worth, your abilities, your potential. They will often disguise this as their objective opinion, but invariably it has a political purpose – they want to keep you down.
 Robert Greene