Then, today, I go all the way through practice, and my mind goes, "How did I do that? Where did that come from?"
Sometimes, I answer myself, saying, "I don't know how I did that, but I am very grateful for it. Thank you, thank you, thank you."
The only way I can make sense of it is that there's more than "me" doing the practice. That is, obviously my mind isn't doing the practice - well, the physical part, anyway... my mind IS practicing - practicing getting out of the way so I can focus on breathing and being.
So, maybe... Strength is Being.
Strength is Ujjayi breathing.
Strength is Devotion.
Strength is Sthira - sukham asanam (a pose that is steady, still, alert, calm, and relaxed, or with-ease).
Strength is flexibility, not just of body, but of mind. The willingness to observe the mind and its wanderings without letting the wanderings take over and change being.
Strength is Now - not what you had in the past or what you will develop in the future; it's here in you Now.
Strength is hope.
Strength is possibility.
Strength is being vulnerable.
Strength is turning upside-down.
Strength is taking rest. Often.