That one Asana and debate on practices.

Yesterday I headed into Atlanta for Ashtanga Primary class. It was a nice sized class and I built up a good sweat! I made it through but towards the end I was not jumping back or through. I used what energy I had left for the asana itself.
I've been practicing Head Stand (Sirsasana) for almost a year and just can't get it. I can use the wall, but with out the wall...forget it!
I try the tips my teachers provide but no luck.
I don't know what it is! I know it just takes time, but almost a year of practice and very little progression. I also messed up my shoulder last night while practicing at home (just sirsana)
I think I just rocked my weight to one side. It will be okay, they muscle is just a little sore and tight today.
You know in your practice that one asana that you just can't get through. That you dread through your entire practice, you dread it yet you want to work on it all at the same time!
Sirsana is that asana for me.

Tonight I am hoping to make it to Mysore and will once again work on this asana.

On the Subject of types on Practices
There are some debates, comments and suggestions from teachers when you bring up the different types of Asana Practices.
One I've often heard: "Stick to one style of Asana practice, don't skip around." (that is a summarized quote)
Pretty much I gather they figure if you stick with on practice you can better "master" it over time.
I guess when you have that "teacher" that you know will guide you it is easier to dedicate your practice to one style. For me I am kind of "floating" out there. Unsure of who my teacher will be and what style I truly want to follow.
I adore the Ashtanga Practice as taught by Sri K Pattabhi Jois and I also really find a connection with Dharma Mittra. His teaching method, his foundation, his flow. It all makes sense.
I guess I pose the question to other yogi's out there how you feel in regards to the debate on sticking with one style of yoga.
I have 3 dreams:

1. Go to India to practice at the Mysore Shala with Sharath Rangaswamy & Sri K Pattabhi Jois
2. Take the 200 hour teacher training with Dharma Mittra (I think this might be more tangible in the future)
3. One day become a teacher (this is farrr off)

Okay, on with my day. Have a great Monday!