Many men unconsciously stick out their little finger when holding a teacup or something else. This gesture is seen as feminine, or as a habit needing correction, like being left-handed. In fact, it is their unconscious anima at work.
This hand gesture is called the Flower-Plucking Finger in Buddhism: Buddha held up a flower, and Mahakasyapa smiled.
Casting off all false appearances and communicating heart to heart represents compassion. Suppressing that little finger is not a good thing instead.
"Masculinity" is social, just like "femininity." If a girl behaves like a boy, she will likewise face many strange looks.
Both the anima and animus have light and dark sides. The deeper a man identifies with his persona, the darker his anima becomes. Take the witch hunts of the Middle Ages: the author of Malleus Maleficarum believed himself to be as straight as straight could be and could not tolerate the slightest feminine trait. That was why he hated women so much that he wanted to physically eradicate them.
Men were generally more tolerant of women; women were especially vicious toward other women. Hera in mythology was an example, though nothing illustrated it better than the so-called "mother-in-law and daughter-in-law relationship" among Chinese women.
The dark anima within that author enabled him to write works that an ordinary man could not.
Jung understood that a "dark anima" could make a man afraid of his wife. Jason of the Golden Fleece had once been an upright and wise leader, but during the adventure for the Golden Fleece, he too became indecisive, obsessed with the pleasure Medea brought him.
If a great hero could not overcome the temptations brought by his persona, his heart would grow weaker and weaker.
A persona existed to please those around one; it was not the true self.