A problem with an animation please help? (not solved)

This is my script, it works fine but the animations is a bit weird...

local player = game.Players.LocalPlayer

repeat wait() until player.Character.Humanoid

local humanoid = player.Character.Humanoid

local mouse = player:GetMouse()



local anim = Instance.new("Animation")

anim.AnimationId = "http://www.roblox.com/asset/?id=1491234078" -- id of animation



mouse.KeyDown:connect(function(key)

    if key == "z" then --Select a button, if you want shift then put 48 in it

        local playAnim = humanoid:LoadAnimation(anim)

        playAnim:Play()

    end

end)

THIS IS THE PROBLEM, the animation plays only in one direction, how do i make it play in the direction you face in... and also, how do i make the animation stop when you hit the ground is there a way to make this"? does the animation need some kind of werd stuff??