This goes back to something I posted on Facebook a while back, but the bhavans are at the very root of progress in our practice! Take some time to read and observe your practice.

The Bhavanas - these are the four qualities of the mind that foster growth in your yoga practice.

Have you ever heard that inner voice telling you "I can't do that", "I don't deserve that" or "This I don't like"? Chances are high that you have. These doubts are exactly what nourishes and feeds our inner obstacles to growth. These doubts, or unadventageous inner orientations, act sabotaging to our practice, as they lead us to not practice compassionately enough and make our energies dissipate and get distracted. If we want to cultivate progress in our (yoga) practice, we need to learn to substitute those unadventageous inner orientations with beneficial ones - and this is where the bahavans, the four qualities of the mind for progress, come into play: 
1. Empathy - for your own progress and that of others 
2. Friendliness - Towards yourself and others 
3. Encouragement & Passion - for the path of progressing 
and 4. Allowance or patience - having patience and trusting the progress and that things take time...

When we don't allow the cultivation of these qualities, progress in our practice is difficult. If we want to much and force things, we stay our own's worst critics, let perfectionism sabotage our progress, and possibly get injured along the way. If we slack and don't want enough, we will always find excuses and reasons why we cannot practice and our progress will stop.

Wanting to share my yoga notes from the wonderful two weeks practicing under David’s guidance and being among other ashtanga enthusiasts.  May be these notes can help your practice in some way. 

Overall conclusion of my time practicing with David: I want more! Respect and thanks to David and Joy for sharing their resources and providing this fantastic time of learning for us.

Bandhas – always a hot topic, no surprise it came up during this asana kitchen!

David spend some time getting into uddiyana bandha and explaining how it can be better developed and accessed.  One way to develop more awareness for uddiyana bandha is to practice the uddiyana kriya before asana practice or just after headstand. (See here for uddiyana kriya practice)  David kept mentioning that it is very beneficial to practice uddiyana kriya daily.

Then, downward dog is a perfect pose to access uddiyana, especially when bending the knees.  And, all inversions accentuate uddyiana (so next time in halasana - bring the awareness to uddiyana, don't forget to set up the pose first, engaging thighs and legs, inwardly rotating the thighs and lifting through the buttocks)

Ever felt that you are taking it a bit easy at certain parts during the practice? (e.g. you loose focus at certain points during the practice, in certain poses you may not try with all effort, or as the practice progresses you start "pacing" yourself in the vinyasas, ... you may get the point.)

David explained that such observations are very informative about one's approach.  It's good when you notice that you are doing this (loosing focus, pacing, softening the practice, etc.). Don't go about it punishing yourself for your limitations in the practice, e.g. "taking is a bit easy here and there" BUT notice your reaction when you observe that your limitations. Investigate whether you can accept and live with these limitations or whether you want to change them.  If you want to change those limitations, you need to ask yourself what you can do to change the situation. May be you need to change your intention, commitment, perception, something in your life, or may be something else.