It's actually taken from the writings of Afred Adler.  His take on the separation of tasks was that we should consider that what other people think of us is none of our business.  Since its inlikely that we can influence it anyway, what not give some mindful thought to whether this is true or not. More to the point it's not about truth, it's about what suits your own view on how to transform a life from one of anxiety and depression, to one of calm acceptance that you are a worthy human being regardless of what you believe others might think.

Wouldn't it transform your life if you were to coach yourself into accepting that you are plenty good enough just as you are?