Haven't been misgendered since I started presenting in girl mode (except, on occasion accidentally by people who knew me before transition). So I guess I passed first time out of the gate. But I would echo what Jessica and Jill said above. You have to feel confident in yourself and not care what others think otherwise you will look like a rabbit in the headlights.
A lot is about presentation too, I use a wig and most likely will have to the rest of my life, it is the one prop I do need to help me pass. Without Hillary I wouldn't pass at all. So I'd say that if you feel you do not pass, what prop/s might you need to get over the line? Sure, some feel you're not truly passing until you can walk out the door in jeans, a tee and no makeup and be called "she", but for many of us if we're waiting for that golden moment as our validation of being able to pass it may be a long time coming, if ever. Why wait when, with a little help from whatever prop you need, you can be living as the person you want to be?