The "Poker Face" singer struggles to cope with homesickness while out on the road but has now learned to accept her "darkness."
She said: "The lowest point is loneliness, being on the road. I have a chronic sadness that recurs. The lowest point was in Australia in May. I was overwhelmingly sad, and I didn't know why because I had all these things to be happy about."
Despite her black moods, the singer says her emotional state inspired her to write her best ever material.
She added: "I went to the studio and played for hours and I wrote what is going to be the greatest record of my career, a beautiful song about my father."
"I remember watching the mascara tears flood the ivories and I thought, 'It's OK to be said.' I've learned to love my darkness."
