I carry, and drawing on an already drawn gun is almost always unwise. At that point you've already failed at situational awareness. Maybe you will get a chance to draw your weapon if the attackers attention and gunpoint move away from you. Better just to comply and try to be a good witness, unless you have no other choice.
The key is to be aware of your surroundings in the first place. Don't let anyone run or drive up on you without at least being ready to pull your weapon. Move away from the threat and create defensible space between you and them. I like to pocket carry in a hoodie or jacket in bad neighborhoods. You can have your pistol in hand and be ready to pull it or shoot through your pocket if you have to.
I got carjacked once in a drive-thru before I carried. I was being stupid and a guy with a knife was leaning inside my window before I even saw him. He caught me with my window rolled down, doors unlocked and car in park. I should have been watching my rear view mirrors, but I wasn't. Now I get really uncomfortable if someone moves into my blind spots either while I am driving or walking, so I will turn to look at them and let them know I am aware of their presence.
It kinda sucks having to always worry about personal or vehicle defensive space and who might be in it, but it becomes second nature after a while. Just remember to be polite to everyone because 99.9% of the people who walk into what we call our defensive space aren't planning on causing any trouble. It's not their fault if we choose to be hyper-vigilant just in case.
Remember that carrying a weapon makes you responsible to be polite, keep your ego in check, and walk away from potential trouble if you can.