From Mushin:
We call these Encouraging Words, a phrase Aitken Roshi used to refer to his short prompts for practice. The most encouraging word that I know is metta, lovingkindness. The practice of metta had become an essential element for practicing in this cultural context, where so many of us are hounded by an inner, critical voice. The metta phrases invite us to be free from anxiety and fear, to have physical and mental well-being and to be at ease. This may even be the very first time that you’ve given yourself permission to experience these states of mind and body. Inner permission to change our mind is the necessary condition for actually experiencing it.
Self-criticism binds our attention to the thinking mind, tightens the body and restricts heart energies. Such self-reproach thwarts any opening up that concentrated, relaxed attention allows for. If you’re sitting in thoughts of self-reproach you are reinforcing an endless cycle of self-suffering. You don’t deserve this. It doesn’t help you. It’s important for us to recognize our own forms and content of self-criticism. The voice of our inner critic does not necessarily show up as a spoken, articulated criticism. Sometimes it’s detectible as a form of tension, in the gut, in the heart area, jaw, tightness around the eyes, in the shoulders. These are samples, but you may recognize that you hold the criticism in your own other, unique way. Once we wake up to how we believe this self-critical attitude without question, we can begin to question it, learn its source, and go beyond it. Then zazen truly unfolds. Dropping self-consciousness becomes a possibility.