just get better at timing it, and think ahead about what move you're doing next.
Assuming you can charge the exceed bar to 1/3 everytime, and the only time you ever drop is if you're going for a max act and you screw it up, don't go for the max act unless you are actually in need of it (I don't have the game installed but for moves like calibur and streak you will want all 3).
If you have 3 bars charged and you are only using a swing that will cost you 1 charge, or a combo of moves that all require 1 charge each, just make sure you get the single exceed every time, since this is much easier than a max-act. You should never be on 0/3 unless you use a triple and miss time the max act.
Basically it's a simple strategy to being careful with your exceeds.
I can explain it a bit better if you don't understand this, but the basis of the whole thing is simply practice and timing, some people are just better at it that others. When I play I can hit the 1/3 on every move pretty much 100% of the time, and have practiced getting the max act with all the moves that cost 3 bars, and with the moves at the start of combos extensively, so making sure my sword is charged most of the time.