So, yes, I have posted this pose several times, getting it on and off, and often for dissatisfying short periods of time (ten seconds is what a phone timer is normally set to:)
But today, I proudly claim with that I am very comfortable in this pose. That is because I decided, as I am wont to do, work around the pose by cleaning up its preparatory poses.
So, whole of last week I worked on the lolasana (cradle pose), with the lotus leg lock. I tried to chunk it up, and hold it overall for one minute, which is why today I can so the Pose of Self-restraint (Brahmacharyasana means that, really)
I found out this humbly enough, while demoing it to a male student who was not able to do the squatting crow (that's what I call the dwipada bhujapidasana/two-legged shoulder pressing pose).
I did the preparatory leg folded at the knee and lo, when opened the legs, it was up in Brahmacharyasana. I held it long enough, despite the overwhelming surprise, to determine if I can actually do it.
What you need:
* Upper back strength.
* Core strength.
* If you do not have either (and you will be surprised how elusive and difficult to cultivate either are, especially if your bones are dense and your are super- muscled -- because the heaviness of your health itself will drag you down, and no jokes) you must spend considerable amount of time in lolasana/cradle pose with the knee bend inwards (if you can't do the lotus) or the lotus-leg-locked cradle pose.
* Comfort in ekapada bhujapidasana (one-legged shoulder press pose too)
* Also ability to be comfortable when retaining breath -- because as a beginner in some poses like this it would be difficult to breathe because the breathing will break the pose. So being able to do a demanding muscular move without breath and be comfortable enough, that is very important.