5 ideas
In the beginner's mind there are many possibilities, but in the expert's there are few. Accumulated expertise narrows perception into fixed categories and self-conscious achievement. The practice is to keep meeting each activity, including one done thousands of times, with the empty, receptive attitude of the first time.
Students naturally want to be the best horse. Suzuki reverses this: the worst horse, the one who struggles most, can be the best student, because difficulty forces the deepest engagement with practice.
To control your sheep or cow, give it a large, spacious meadow. Suppressing thoughts during meditation makes them stronger. Letting thoughts come and go while simply watching them lets them settle on their own, so real control comes from giving space, not from restraint.
Sitting in the correct posture is not a technique for reaching some later enlightened state. It already is the expression of Buddha nature, so practice and attainment are one. Practising with a goal of gain turns zazen into another form of striving and loses its point.
Half-hearted action leaves a residue of the self: lingering thoughts, comparisons, and regret that clutter the next moment. Total absorption in the present act lets each activity finish cleanly.