I suppose now I should actually answer the original question.

Over the years I probably tried anal sex 20 times, and was successful 10 of those times. I couldn't figure out why sometimes it felt great and sometimes hurt too much to bear...same amount of lube, same position...no clue.

When I finally began to accept and integrate my submission into my life, I figured it out. Anal sex is so personal, so private, so 'dirty', and yes, painful...that my mind has to be in that submissive 'head space' to start with. Then, that feeling of pain when he first begins to push in...the fullness and ache when he's fully in my ass...I feel it from my head to my toes, like an electric charge throughout my whole body, and the feeling of utter submission grows and grows and I never want it to end.

It's even better when He ties my hands behind my back. And whispers in my ear, "You'll do anything for me, won't you?" And I can only say yes, and beg for more.
Harder. Deeper. Please.