There are two fighting Arcs. Yours and your opponents. As an initial defence it is the intention of yourself to keep outside of your opponent’s ‘fighting Arc’, but when you are unfortunate to be in their ‘fighting Arc’, then you must take advantage of your own fighting Arc and proceed accordingly. This sound an anomaly, let me explain.
If you wish to be in a position of strong defence then you need to be outside your opponent’s ‘fighting arc’, this is achieved by backing away or making them move away.
As they approach then they bring their fighting arc into position. It is your own fighting arc that you must take advantage of. When your opponent enters your fighting arc you must react immediately.
If not, then your opponent’s fighting arc will come into play and you will lose.