Tension in the string hand comes from shooting off the pads, and not hooking on the string. Shooting off the pads creates a curve, and when you hook on the back of your hand and fingers are straighter.
And, if you are hooking and still plucking, you are either 'telling yourself' to let go....or your elbow is not back far enough to create back tension.
Least that's my take on it.
The more you shoot, with a proper grip on the string and proper back tension, your release will just 'happen' when your brain registers 'on target'.....just like you don't tell yourself to let go of a baseball or football.