I took a lot of elective poetry classes as an undergraduate - just reading, not composing - because I love good poetry and I love trying to get inside the poem and see what makes it work. I've always remembered one comment that a professor of mine made about writing poetry. He said that once he had asked another poet whom he admired, "How do you know when you've done enough revising and the poem is finished?" The other writer answered, "Well, if you're lucky, at some point when you change a word you will hear a click!, and that's when the poem is done."
This reminds me of my favorite quote about sculpture. Not sure who it's attributed to, if anyone, but the story is that a bystander asked a great sculptor how he had created this beautiful, life-like sculpture of a horse. He said, "It's easy. I just chip away everything that doesn't look like a horse."
Different mediums, but same idea: the idea that works of art already exist in the universe somewhere, in their ideal platonic forms, and the work of the artist is simply to unearth the poem or the horse, to conduct it into the physical world, to realize it, to set it free.
I like to think of yoga asanas this way as well. Each asana has an ideal, platonic form which exists, whether you are executing it at the moment or not. And the ideal form looks different for every person, on every body, but it is always the same. Hips and shoulders in line, arm stretching forward, forehead touching knee, spine twisting from coccyx to neck... these are all parts of the form of the postures, and these are the things that we always are trying to attain.
I wrote to Hannah that I often think of the postures like puzzles. (I've been thinking in puzzles since before I can remember.) We have to study the details. The details are our lifeblood. There is no forest without the trees. But it's like piecing together a puzzle. In order to get anywhere, you have to focus closely on the intimate details of each individual piece: its shape, its shading, its light. You study the pieces and you study their relationships to each other, and slowly, painstakingly, deliberately, you put them in their place. There is no other way to do it. But then, at the end, once you've considered each and every detail, the final piece clicks into place, and you are looking at a complete landscape.
So sometimes, if you are lucky, the postures are this simple.
Sometimes it is just a matter of chipping away everything that doesn't look like standing bow.
And sometimes, after you've studied and memorized every detail, you can let go of the details and see the big picture, and then simultaneously, without conscious thought, just lock your knee, charge your body forward, kick back as hard as possible, bring your body all the way down parallel, aaaaand... CLICK. There's bow, balanced, suspended, weightless.
That's what it means to "lock it." You turn the key, aaaand... click. The posture exists. Not all the time, not even most of the time, but when it happens... oh, that's just the best.