Just an inch of proper movement to close the gap or move within the gap can be the difference between victory or defeat. Proper spacing allows you to flow with your opponent without you getting locked up in your stances or handwork. In fact it makes them work even better.
Drills with a partner for proper footwork are paramount and most styles have their own drills to keep spacing and/or to control the gap. From my experience, the person who controls the gap wins, but the gap is also a very tenous place to be. It is in constant flux and you must be able to make adjustments accordingly. If you don't your opponent will...so in an altercation, it is as important to know how to enter the gap and control your opponent in it. Practice, practice and more practice is the only way to develop this skill. It can't be done by intellectualization.
Hands palm to palm,