Every time you attack, you are open ...
Put another way, if you can get them ... they can get you, and the thing they can get most easily is the part of you that is closest to them, which, in all probability, is your weapon hand.
Sword designers know this of course, so any weapon designed for combat usually has some kind of hand protection, a guard of some kind. This can take the form of a cross piece, a basket, a cover, a thumb guard, or a curve in the blade that deflects cuts away from the hand.
(Of course even with a hand guard the arm is still a target, it's just a little harder to get to as it is further away and behind an obstacle (the guard itself).)
In the Visayan style I practice, the weapons generally have no hand guard at all, because it is a system designed for 'daily carry' blades - Bolos, Goloks etc - and these are utility knives/tools. What this means is, because the piece of kindling, coconut, or chicken you are cutting is not going to cut back, they are deemed unnecessary.
This means that when you use the same blade in a combative setting, the first necessity is to protect is the hand, because basically, no hand = no weapon.
So the ability to target the hand and to not be a target is the first problem to solve, and the first game to play. It is part of our First Flow - playing at the edge of the range and 'picking' targets whenever they appear.
Learn how not to get hand tagged.
Learn to tag the opponent's hand.
Learn to not get tagged AND tag at the same time.
Learn how to use body angle and weight shift instead of stepping to play the margin. Also, learn the limits of this game - when to bait a tagger, and when it is too dangerous and what new game to play.
The most important pieces here are understanding range, but also understanding repetitive rhythm and the ability to mirror/read you opponent's patterns, whilst making your own movement as unreadable as possible. The ability to be accurate is also an absolute necessity.