Stuff like this (breaking in a new cable/string) is a perfect time to blind bale shoot
Get right up on the target, close your eyes and work on the feel of the shot. Kills two birds with one stone-plus if the bow is out of timing/not tuned up right, then you won't get flustered by it not quite shooting right- it might get to ya a little if you were shooting at 15 or 20 yards even when you know you are just trying to cycle the cable/string.