"Good, strong base, hard to take you down - but when you're not just attacking, but being attacked, its too broad a profile. From that stance, shift your left leg back about a foot behind your right, out at a 45 degree angle, turn your body with it - it'll keep your stability, you keep your weight on the balls of your feet for quick action and reaction, the same way, but you provide a narrower attack profile and are more stable against frontal assault - the most common. Then bring your right hand up to just under your chin level, keep your left hand down."