Dumb Luck
She puts her hands on your shoulders to steady herself, leans in with her hot breath in your ear and whispers, "Stay up this time."
As her breath leaves you with a tingling chill in your ear she fully extends her foot back and swings it forward with all her might right into your balls yet again.
WHACK
You wobble slightly but you feel that she is leaning on you so heavily that she will fall if you do and so you straighten out and fight through the pain... for her you realize. The aching is powerful and nauseating but you flex your core and embrace it, tears rolling out through your clenched shut eyes. Your balls are throbbing now so hard that the sensation almost feels pleasurable and you're suddenly overcome with joy for a moment despite the pain.
You feel satisfaction at finally living out your fantasy and measuring up so well in the process. With all of your might you hold your body still in the position your Goddess wants you in.