Sacrum os

I've just finished working with John.
Amongst other things we discussed the importance of having the bum (sacrum) in.
It became clear (it was clear before but this jogged the memory) that this is the single most important aspect of the work we do.
Everything else stems from that, including going forward: it is the sacrum os that drives forward (the sacred bone - there must be a reason it is so called).
Unfortunately the sacrum doesn't generally want to be in so this principle requires constant attention (care & attention as fishermen & poets - the sort of vigilance that results in death if relaxed): attention to the aforementioned energy-circuit of down the back & up the front.
Let the energy that flows up flood into your face & heart like a sacred mist (John's phrase) - give it respect & reverence; in a way it's the best part of you.

As a teacher the importance of this principle cannot be stressed enough.
Those that refuse this never really learn because they are refusing to face up to what life presents - ultimately life itself (destiny).
Not having the sacrum in is the ultimate act of avoidance.
All problems (not just TaiChi ones) can generally be traced back here.
But beware. If you have a chronic problem here then be gentle because there is bound to be some psychological or emotional trauma attached which needs to be addressed. When the armour is removed the raw bite of reality can be overwhelming.

It is important to try to develop some awareness in the sacral area.
Try exercising it (figure of eights) and getting a fellow student to gently place their hand on the area as you work.
Getting the sacrum in is a long project (my teacher used to say 10 years minimum) and will gradually refine for the rest of your life if you allow it.
It is the natural place of sobriety & ruthlessness, two of the most important qualities to cultivate as they are the bedrock of courage - the energy that sustains commitment and encourages those leaps of faith required to scale seemingly impassable obstacles to becoming a better person.