If you want your children, your wife, and your friends to live forever, you're being foolish. You're wishing for control over things that aren't up to you. You're wanting what belongs to others to be yours instead. Same thing if you want your employee to never make mistakes — you're being foolish. You're wishing that human flaws weren't human flaws. But if you want to avoid disappointment in what you desire, that is up to you. So focus on what you can actually control. A person's master is whoever can give or take away what that person wants or fears. If you want to be free, don't want anything that depends on other people. Don't try to avoid anything that depends on other people. Otherwise, you'll be a slave.
If you wish your children and your wife and your friends to live forever, you are foolish, for you wish things to be in your power which are not so, and what belongs to others to be your own. So likewise, if you wish your servant to be without fault, you are foolish, for you wish vice not to be vice but something else. But if you wish not to be disappointed in your desires, that is in your own power. Exercise, therefore, what is in your power. A man’s master is he who is able to confer or remove whatever that man seeks or shuns. Whoever then would be free, let him wish nothing, let him decline nothing, which depends on others; else he must necessarily be a slave.