How do I stop an animation from playing?

How would I stop an animation without making another animation? I tried anim:Stop() but it didnt work.

local Player = game.Players.LocalPlayer
Mouse = Player:GetMouse()
play = false

Mouse.KeyDown:connect(function(Key)
	if(Key:lower() == "f") and play == false then
		anim = Player.Character.Humanoid:LoadAnimation(script.animTest)
		anim:Play()
		Player.Character.Humanoid.WalkSpeed = 20
		play = true
		
		if(Key:lower() == "f") and play == true then
		anim = Player.Character.Humanoid:LoadAnimation(script.animTest)
		anim:Stop()
		Player.Character.Humanoid.WalkSpeed = 16
		play = false
		
		end
		end
end)

I'm not sure if you're wanting it to be timed; so here is what I came up with so that after a certain about of time; the animation will stop itself instead of having to KeyDown again. If this isn't what you wanted, you can let me know.

local Player = game.Players.LocalPlayer
Mouse = Player:GetMouse()
Play = false

Mouse.KeyDown:connect(function(Key)
	if(Key:lower() == "f") and play == false then
		anim = Player.Character.Humanoid:LoadAnimation(script.animTest)
		anim:Play()
		Player.Character.Humanoid.Walkspeed = 20
		Play = true
		wait(5) -- Change this value to whatever you want
		anim:Stop()
		Player.Character.Humanoid.Walkspeed = 16 
		Play = false
	end
end)

You're doing it correctly. anim:Play() Plays it.. anim:Stop() Stops it. Works for my animations. Probably other error in the script.