Why did vincant vango cut off his own ear?

He never really said a reason, but he did suffer from many mental health issues such as Temporal Lobe Epilepsy, Bipolar Disorder, Anxiety, Depression, Hypergraphia and Mania. On top of this he also suffered from Lead poisoning, Thujone poisoning (from the large amounts of absinthe he drank), and sunstroke (from his many hours and sometimes days out in the sun painting fields in the South of France).