How can I prevent this script from running when the player keeps pressing z?

me = script.Parent.Parent.Parent
player = script.Parent.Parent.Parent
function onKeyDown(key) 
key:lower() 
if key == "z" then 
enabled = true


function Talk(msg)
game:GetService("Chat"):Chat(player.Character.Head, msg, Enum.ChatColor.Blue)
end

  local player = game.Players.LocalPlayer
    if player == nil then return end

    enabled = false
        Run = game:GetService("RunService")
            for i = 1, 3 do
                Run.Stepped:wait(0.005)
            end

        Talk("Sky Dragon's Healing Spell!")

    MagicSym = Instance.new("Part")
    MagicSym.Parent = me.Character
    MagicSym.Anchored = true
    MagicSym.CanCollide = false
    MagicSym.formFactor = "Symmetric"
    MagicSym.BrickColor = BrickColor.new("Teal")
    MagicSym.Transparency = 1
    MagicSym.Name = "MagicSym"
    MagicSym.Size = Vector3.new(10, 1, 10)
    MagicSym.TopSurface = "Smooth"
    MagicSym.BottomSurface = "Smooth"
    MagicSym.CFrame = me.Character.Torso.CFrame*CFrame.new(0, -3, 0)
f = Instance.new("Sparkles", MagicSym)
f.Color = Color3.new(255, 255, 255)
d = Instance.new("Decal")
d.Name = "Circle"
d.Parent = MagicSym
d.Face = "Top"
d.Texture = "http://www.roblox.com/asset/?id=214848485"
p = Instance.new("Decal")
p.Name = "Circle"
p.Parent = MagicSym
p.Face = "Bottom"
p.Texture = "http://www.roblox.com/asset/?id=214848485"
l = Instance.new("PointLight", MagicSym)
l.Brightness = 10
l.Range = 10
l.Color = Color3.new(255, 255, 255)

wait(1)
MagicSym:Remove()

wait(10)

        j = me.Character.Head
        k = me.Character.Torso
        q = me.Character["Left Arm"]
        w = me.Character["Left Leg"]
        e = me.Character["Right Arm"]
        r = me.Character["Right Leg"]

        me.Character.Humanoid.Health = me.Character.Humanoid.Health + 10
        wait(1.5)




        for i = 1, 3 do
        end
        wait()

enabled = false
    end
    wait(10)

enabled = true
end

function onSelected(mouse) 
mouse.KeyDown:connect(onKeyDown) 
end 

script.Parent.Selected:connect(onSelected)