As for the application of this concept to one keeping his garment below his ankle, it could be understood on the basis of the action not being a momentary one whose effect is long lasting (like shaving the beard), instead it is an action that repeats itself , allowing one to raise it at any second, so the continuous leaving of it, is in reality continuous perpetration of the action of keeping it below the ankle. This wouldn't apply to the beard, as it doesn't have this tajaddud (continuous repetition) in it.