How do I make the character knockback only go backwards of the character?

So I have made a script that is supposed to knock a character backwards when they get damaged. When facing the right direction, the character actually gets knocked backwards. When facing the opposite, it gets knocked forwards. How do I make it that the character always gets knocked backwards of themselves?

 local ReplicatedStorage = game:GetService("ReplicatedStorage")
p = ReplicatedStorage:FindFirstChild("YellowPoof")
local tweeninfo = TweenInfo.new(0.85)

local ts = game:GetService("TweenService")

local goal = {}

goal.Size = Vector3.new(11, 11, 11)

goal.Transparency = 1

db = true

local Health = script.Parent.Humanoid.Health



function onHurt()

    if db == true and script.Parent.Humanoid.Health < Health then

        db = false

        local humanoid = script.Parent.Humanoid

        local p2 = p:Clone()

        local tween = ts:Create(p2, tweeninfo, goal)

        p2.Parent = humanoid.Parent.LowerTorso

        p2.Position = humanoid.Parent.LowerTorso.Position

        tween:Play()

        local animation = humanoid:LoadAnimation(script.Animation)

        animation:Play()

        humanoid.WalkSpeed = 0

       -- Line I need help with!!
        script.Parent.HumanoidRootPart.Position = Vector3.new(script.Parent.HumanoidRootPart.Position.X,script.Parent.HumanoidRootPart.Position.Y,script.Parent.HumanoidRootPart.Position.Z-5)

        wait(1.85)

        humanoid.WalkSpeed = 19.5

        db = true

        end

     end

script.Parent.Humanoid.HealthChanged:Connect(onHurt)