How do I get a GUI Tween to work after a player resets?

I have a script that Tweens the size of a GUI. The GUI Tweening script works at the time that I join, but when I reset my character and try to hold B to tween the GUI after resetting, nothing happens and I get two error message for the tweens. "Can only tween objects in the workspace" line 68 and 77

-- Script made by AltNature / Mr_Quarter#2828



        -- // VARIABLES \\ --

local player = game.Players.LocalPlayer
local runservice = game:GetService("RunService")
local uis = game:GetService("UserInputService")
local runANIM = "http://www.roblox.com/asset/?id=2111751699"
local walkANIM = "http://www.roblox.com/asset/?id=2111623526"
local staminaBar = player.PlayerGui:WaitForChild("StaminaGui"):WaitForChild("NoStamina"):WaitForChild("behind"):WaitForChild("ImageLabel"):WaitForChild("bar")
local money = game.ReplicatedStorage.MoneyValue
local moneyDisplay = player.PlayerGui:WaitForChild("Money"):WaitForChild("ValueDisplay")
local breathBar = player.PlayerGui:WaitForChild("BreathGui"):WaitForChild("NoBreath"):WaitForChild("behind"):WaitForChild("ImageLabel"):WaitForChild("bar")
local check = true


        -- // MONEY \\ --
runservice.RenderStepped:Connect(function()
    moneyDisplay.Text = ('$'..money.Value)
end)


        -- // BENEFITS TO DEVELOPERS \\ --

if player.Name == "AltNature" then
    money.Value = 999999999
end
        -- // FUNCTIONS \\ --

function increaseSpeed()
    player.Character.Humanoid.WalkSpeed = 27
end

function decreaseSpeed()
    player.Character.Humanoid.WalkSpeed = 16
end

function activateAnimation()
    player.Character.Animate.run.RunAnim.AnimationId = runANIM
end

function deactivateAnimation()
    player.Character.Animate.run.RunAnim.AnimationId = walkANIM
end

function tweenStaminaBar()
    staminaBar:TweenSize(UDim2.new(0.854, 0,1, 0), 
        Enum.EasingDirection.In,
        Enum.EasingStyle.Sine,
        1,
        true)
    end

function normalStaminaBar()
    wait(1)
    staminaBar:TweenSize(UDim2.new(1,0,1,0),
        Enum.EasingDirection.In,
        Enum.EasingStyle.Sine,
        3,
        true
        )
end

function tweenBreathBar()
    breathBar.Visible = true
    breathBar:TweenSize(UDim2.new(1, 0,1, 0),
        Enum.EasingDirection.In,
        Enum.EasingStyle.Sine,
        6,
        false
        )
end

function normalBreathBar()
    breathBar:TweenSize(UDim2.new(0,0,1,0),Enum.EasingDirection.In,
        Enum.EasingStyle.Sine,3,true
) check = true
end


       -- // EXECUTION \\ -- 

    --/// Section 1, Sprinting \\\--

uis.InputBegan:Connect(function(input, gp)
    if input.KeyCode == Enum.KeyCode.LeftShift then
        if not gp then
            increaseSpeed()
                activateAnimation()
            end
        end
end)

uis.InputEnded:Connect(function(input, gp)
    if input.KeyCode == Enum.KeyCode.LeftShift then
        if not gp then
            decreaseSpeed()

                deactivateAnimation()
            end
        end
end)

     --/// Section 2, Breathing \\\--
local check = true

uis.InputBegan:Connect(function(input, gp)
    if input.KeyCode == Enum.KeyCode.B then
        if not gp then
            if check == true then
            player.Character.Humanoid.WalkSpeed = 0
            --/ / / Breathing requires some stamina \ \ \--
            if staminaBar.Size == UDim2.new(1,0,1,0) then -- makes sure that the player
                -- can't play with the tween
            tweenStaminaBar() --subtract stamina a.k.a. make the bar's length
            --shorter

            normalStaminaBar() -- this takes 4 seconds.. the stamina recharges in
            --this time
            end
            print("Stamina Bar Decreased.")
            check = false
            end
        end
    end
end)

uis.InputBegan:Connect(function(input, gp)
    if input.KeyCode == Enum.KeyCode.B then
        if not gp then
            if breathBar.Size == UDim2.new(0,0,1,0) then
                tweenBreathBar()
            end
        end
    end
end)

uis.InputEnded:Connect(function(input,gp)
    if input.KeyCode == Enum.KeyCode.B then
        if not gp then
            normalBreathBar()
            player.Character.Humanoid.WalkSpeed = 16
        end
    end
end) 

Help is appreciated, the script is located in StarterPlayerScripts and is a LocalScript