Epictetus describes what ails so many of us - why we are not wise. The reason: "you are frequently dazed or disturbed by certain sense impressions whose appearance of truth gets the better of you. Sometimes you think that some things are good, then you consider the same things bad, and later you decide that they're indifferent. In other words, you're subject to sorrow, fear, jealousy, anger and inconsistency" (verse 6).
People can have similar views of their friends or family. One minute they may be kind and loving, the next moment there may be raging jealousy and hate. How can this be true friendship and love? It can't, because the people involved have placed their self-interest in externals. History and literature are scattered with examples of people acting badly towards each other because of self-interest in externals.
HOWEVER, "if you identify self-interest with piety, honesty, country, parents, and friends, then you are all secure" (verse 18). "Only if [you] identify with [your] will can [you] be someone's friend - or son, or father - in the true sense, because only then will [your] self-interest be served by remaining loyal, honest, patient, tolerant and supportive, and by maintaining [your] social relations" (verse 20).
The simple test of true friendship: "ask whether they put their self-interest in externals or moral choice" (verse 26).
"If any of you are serious about being a friend, rid yourself of such attitudes, condemn them and drive them out of your mind" (verse 34). Examples of "such attitudes" are: placing your happiness and self-interest in material things and externals - putting health, wealth, beauty, status, etc. above and before virtue.
Epictetus reminds us to be gentle with those who still may hold externals above virtue. "Never be harsh, remember Plato's dictum: 'Every soul is deprived of the truth against its will'" (verse 36). This attitude and approach is a very forgiving (also a virtue) outlook on life and people. It gives others the benefit of the doubt and assumes the best of others as a default.