The reason Stanley decided not to fall in love with a woman was that all women were poison. A poison that will kill you slowly without you knowing it.
But the truth is... the main reason is that Stanley is a coward. He was afraid of falling in love... He was scared of being betrayed.
The image of his mother, who often brings her new lover home, haunted him every night. When his father caught her in the act, his mother cried for forgiveness. Because the father loved his wife so much, he forgave her. Unfortunately... his mother didn't regret it and kept bringing home with a different man.
At some point, his mother did something unforgivable. She had sex with her lover right before his eyes, poisoning the innocent brain of a child who was still not ready for the harsh reality.