Confidence is everything.
If you lack confidence then you get nothing, you will not prove you are dominating thus causing you to fail before you even begin. You must take control, absolute control even if she is a strong one, you must be stronger and take that which you know shall be enjoyable. Allow nothing to get in the way, have a safe word in case it goes too far but otherwise do not take no for an answer. Every action, every movement must be done with purpose, control and absolute conviction. If you do not have the fire in your eyes you will not inspire of her your lust and desires.
It all comes down to how you are.