It's all about angles and positioning, folks. You see, when an attacker approaches, you want to be at an angle to them. Not directly in front, not directly behind, but at an angle. This will give you just enough time to... well, let's just pretend you have a good reason for not moving.
Also, keep your hands up. Not in a surrender pose, but in a "I've got this, pal" pose. It's all about confidence, see?
Here's a simple exercise to help you find your optimal defense angle: