and you will become friendly with others. This is the merit of Zen practice. But the way of practice is just to be concentrated on your breathing wit… - Shunryu Suzuki

But the way of practice is just to be concentrated on your breathing with the right posture and with great, pure effort.

The true purpose [of Zen] is to see things as they are, to observe things as they are, and to let everything go as it goes... Zen practice is to open up our small mind.

Another mistake will be to practice for the sake of the joy you find in it. Actually, when your practice is involved in a feeling of joy, it is not in very good shape either. Of course this is not poor practice, but compared to the true practice it is not so good.

If we practice hard, concentrate on zazen, and organize our life so that we can sit well, we will find out what we are doing. But you have to be careful in the rules and way you establish. If it is too strict you will fail, if it is too loose, the rules will not work. Our way should be strict enough to have authority, an authority everyone should obey. Thu rules should be possible to observe.
This is how Zen tradition was built up, decided little by little, created by us in our practice. We cannot force anything. But once the rules have been decided, we should obey them completely until they are changed. It is not a matter of good or bad, convenient or inconvenient. You just do it without question. That way your mind is free.