Effortless Effort
One concept from the Zen / Taoist tradition that I've found very helpful in my personal practice is effortless effort or wu-wei, expressed nicely by Carlos Castaneda:
If a warrior is to succeed at anything, the success must come gently, with a great deal of effort but with no stress or obsession.
The phrase teases apart two components of the concept effort: physical and mental. Consider your own associations with words like effort or work. There is both the physical reality of washing the dishes and the mental experience of impatience, boredom, haste, etc. Rarely do we consider that there is a difference between what our bodies are doing and how our minds are reacting, but it's certainly true. Our bodies act in the world, and the sensory impressions of our efforts are synthesized in the brain to create a (nearly) simultaneous moment of mental experience. Significantly, en route to consciousness the incoming sensory data is filtered through our mental habits, beliefs, and moods. This may seem technical, but the implications are vast. Our experience of the world is a product of both the world and whatever mental lens we're seeing it through.
Let's consider the effort of a yoga pose such as Warrior 3. On the physical plane, there is full effort: the muscles work, blood pumps, breathing increases. No way around that. But our inner experience is not fixed. We can react to the intense sensations with fear, grit our teeth and push through with short, panting breaths, expending all our energy quickly. Thoughts spin out of control, lamenting our weakness or poor balance. That's effortful effort.
Or we can allow the sensations to flow by, watch our thoughts but keep bringing focus back to a steady breath, relax our jaws and soften our eyes. If we start to fall, we just fall out of the pose and then come back in without thinking nasty thoughts about ourselves. The mind is gentle yet focused. Muscles work steadily but not aggressively. That's effortless effort. Which sounds more sustainable?
Effortless effort also means making exactly the effort required, and no more. In our "more is better" culture, we tend to assume that working harder and doing more always leads to better results. Not so in yoga. It's true that when we begin and our muscles are untrained, each pose may well require our full effort. But after many repetitions of a pose, our muscles get stronger and more sensitive. We learn just how much energy we need, and it's often less than maximum. Thus I encourage students to notice where they can relax in each pose - even if it's just their jaw. Ultimately, a yoga practice should give you more energy and focus. If you consistently leave class feeling totally wiped out and spacey, that's a sign you're working too hard. By working less, you can be more sensitive to the nuances of the body and breath, and you'll actually go farther and have energy to spare!