In an interview with The Guardian, Stella McCartney described the complexities of her design process, which sound painstaking, thanks to her belief that psychology and clothes are totally intertwined — one misplaced button and who knows how she’ll feel that day. “Fashion is psychology, so there’s a whole holistic sense of self that I’m thinking about when I’m designing," she said. She continued: “If I wear a slouchy jean, that will affect my posture and my whole manner. What I’m projecting will be a reflection of that waistband, a detail you might not even notice.”

That explains why McCartney only wears her own designs. She explicated: