The single most important aspect of the physical aspect of boxing, MMA, street etc. is footwork. It is both your attack and your defense. Understanding how to move your feet properly, and becoming really good at it, will benefit every aspect of attack and defense including defense against takedowns. Your feet should always be moving, even if only a little. Constant adjustments however small. If you set to throw a hard punch it is at the end of a step and the beginning of another one, not even a second is spent with the planted foot. Immediately move off of it to another punch or an angle away from your opponent.