There is really only one rule for Bikram yoga: breathe.
Forget all those other rules.
You've heard those rules, right? Don't drink your water now. Drink your water now. No, not now! Don't touch the door. Ok, touch the door if you have to, but only at this one time. Don't scratch. Don't fidget. Don't flail around. Don't touch your towel. Don't lie down like that when you think you're about to die, lie down the other way. Don't look at anything else in the room. Don't talk. Don't leave the room!!
Yeah, those. Forget about those.
(Obedience school is for dogs.)
The goal is not to have a picture-perfect practice. The goal is not even to stay in the room for 90 minutes, not in every case, not necessarily. The goal is to get the most benefit from the class, by listening, by trying the right way, by always breathing.
And all those other things? The stillness, the control, the etiquette, "discipline"? They can and will happen on their own over time, naturally and organically. And then eventually, in the future, you stay still because you've learned to focus. You avoid gulping your water because you've learned that it doesn't help you very much. You stay in the room because you want to be there.
Forget the rules.
Breathe, and don't worry.
Everything that you seek is coming.