If you are going to criticize yourself every time your mind wanders out of the present moment, well, you’re going to be criticizing yourself a lot.
Maybe it is time to stop berating or belittling ourselves for not living up to some romantic “spiritual” ideal. How about just noticing what is unfolding? When we think we have “blown it completely” by forgetting about the breath altogether during a period of formal practice, how about just bringing awareness to thinking that you “blew it”? That thought is itself a judgment, just one more internal commentary. You haven’t “blown” anything. There is nothing wrong with you. And there is nothing wrong with your mind. These are just judgments the mind is generating in reaction to one experience of your attention wandering away from its chosen object. You will have millions, billions of such moments. They don’t matter, but they can teach us a lot. Can you see that you can dwell in awareness or come back to awareness, at least for brief moments, over and over again, even as the mind goes here and there and is preoccupied with this or that?
In each new moment, we are presented with this option, to see what is actually happening, which we call discernment, rather than to fall into judging, which is usually overly simplistic, dualistic, binary thinking: black or white, good or bad, either/or. Suspending judging, or not judging the judging that does arise, is an act of intelligence, not an act of stupidity. It is also an act of kindness toward yourself, as it runs counter to the tendency we all have to be so hard on ourselves, and so critical.