I have a very similar rule in my life. People can either give you energy or drain it. True friendships of course involve both good and bad over time but it is the net that counts. If someone in your life is constantly leaving you feeling drained, it is better to let go of them politely, regardless of how wonderful the relationship once was. Once you figure out a person as a source or drain of energy, it's very easy to manage the relationship from that point on. Most people just don't feel comfortable coming to such conclusions.
