The good thing about coming to practice regularly is that you end up practicing through the ups and downs of life. When you are rooted in a regular routine of morning meditation or evening asana you can't help but do it even when things are really bad, or when things are really good. When I think back over the past decade of my practice, I think of practicing through break-ups, through moves, practicing on vacation, making it to the mat in India, practicing through health issues. And a great thing about the versatility of a yoga practice is that you can always practice something, no matter your state of mind, state of body.
Some days I seriously don't feel like it. And not always, but sometimes, those are the most fruitful days of my practice.
Now I know that some of you are probably thinking that I obviously practice every day because yoga is my job and that's what I do and so I have to. But it isn't that simple. I think about my personal practice, my personal spiritual quest as somewhat separate from my teaching. I incorporate a lot of my findings into my classes for sure and my training is usually translated right into my teaching. But, my time on my mat and my morning meditation is mine. It's work that I do for me, it's work that I do to actualize my potential, it's work that I do to fulfill my dharma. Being anchored in regular practice is the key for me to living in the middle ground.
In the Yoga Sutras the sanskrit term for diligent, continuous practice is abhyasa. (The following translations and explanations are taken or adapted from Nicolai Bachmann's The Yoga Sutras. It's a great resource with a workbook, flashcards and several cds explaining the philosophical concepts. I would highly recommend it for anyone interested in deepening their understanding of yoga philosophy)
There are several sutras which explore the concept of abhyasa.
The most commonly cited is sutra 1.12:
abhyasa vairagyabhyam tat nirodhah
The stilling of the vrtti-s (mind-chatter) is due to diligent practice and vairagya or unattached awareness.
Sutra 1.13 goes on to further explain abhyasa:
tatra sthitau yatno 'bhyasah
Diligent practice is the effort put forth to maintain a point of focus.