During a great asana practice, you'll be invited to reach and move towards your edge - listening to the breath as an edge detector so that you know, anymore would be too much, but any less is not interesting enough to keep the attention. This is, to be frank, a kind of controlled tension.
In fact, I believe that in the laboratory of asana practice, that we 'intentionally' create 'tension' through the 'intensity' so that we can pay 'attention' to that moment, and how we relate to that moment. And then, how we relate to our relating to the moment.
Once I've tripped that far down the lane, I've got to go to the foundation, to the root, and to discern what this energetic is. A little amateur etymology here and it comes back to turtles all the way down!
'Intention' - 'Intend' c.1300, "direct one's attention to," from Old French 'entendre', 'intendre' - "to direct one's attention". This comes through the French, from Latin 'intendere' - "turn one's attention, to strain," or literally "to stretch out, extend," from 'in-' "toward" + 'tendere' "to stretch" (we're going to have to go check 'tendere' now, since it's the root of both "attention" and "extend" as well). It was only around the late 14th Century that "intend" began to express a sense of "have as a plan".
Related through the same roots of 'tendere' is 'tenet' - as such: ‘Tenet’ – early 15th century "a principle," or more expansively "a thing held (to be true)". This descends from the Latin ‘tenet’ "he holds," from ‘tenere’ "to hold, to keep, to maintain" and this comes from the Proto-Indo-European root ‘*ten-‘ "to stretch".
Here’s where it get’s interesting – this same root is from the Sanskrit, and the word there is ‘tantram’ "loom," i.e. "tightened or stretched on the loom". The same root goes to Greek ‘teinein’ "to stretch;" ‘tasis’ "a stretching, tension;" ‘tenos’ "sinew and tendon;" ‘tetanos’ "stiff, rigid – think tetanus (lockjaw);" ‘tonos’ "string," and from there to ‘tone’ "sound, pitch."
There you go - a little trip around the language lane and right back to the mat. Turn your attention and your intention into 'stretching' or 'extending' and moving yourself into the loom of tantra. Use your tenacity and your tendons to hold and maintain, create your tenets in your practice by making your intention simply paying attention.
Live on the loom - you move the shuttle, your create the weaving. Sure, the warp is set, but by paying attention to the weft and how you weave your intentions into principles and how you observe your Self in that process, you can make any life, cut from the cloth of choice.
Give thanks and praise!