Strindberg:

Do Not Play With Love

The disciple continued: When a man and a woman unite in love, a single being arises whose existence is in itself pleasurable as long as harmony reigns. But this being is such an extremely sensitive reception device, or coherer, that it is subject to interferences from the currents of others, near and far, a disadvantage that it shares with wireless telegraphy. Therefore, a disturbed relationship between spouses is the greatest suffering that exists, and unfaithfulness is a cosmic crime which leads one or the other party into a perverted relationship with their own sex. If the man casts his feelings towards another woman, the wife is exposed to terrible alternating currents which by turns make her hate and love the woman who is her rival. Often she may make friends with the man’s lover, but more often she gets to hate her. And those who go between two lovers shall not go unpunished, for the hatred they generate is so terrible that they may be paralysed by the discharges and lose their energy and zest for life.

Therefore it is said: Do not play with love.