How to make sprint bar not go negative?

I found a bug that makes sprint bar go negative and still allow player to sprint. How can I remove that?

while wait() do
	if enabled.Value == true then
		if humanoid then
			if humanoid.MoveDirection == Vector3.new(0,0,0) then moving = false else moving = true end
			if tired then 
				ChangeSpeed(exhaust.Value) -- Rest
				Frame.Rest1.Visible = true
				if not moving then
					stamina = stamina + 2
				end
				if stamina > 0 then
					tired = false
					Frame.Rest1.Visible = false
					Frame.GreenBar:TweenSize(UDim2.new(3.5*stamina/875,0, 0,12), "Out", "Quad", 0.1, true)
				end
			elseif running == true then
				if moving then
					ChangeSpeed(run.Value) -- Sprint
					stamina = stamina - 2
					Frame.GreenBar:TweenSize(UDim2.new(3.5*stamina/875,0, 0,12), "Out", "Quad", 0.1, true)
					if stamina == 0 then tired = true stamina = -10 end -- i think this is the culprit, but I don't know a work around it.
				elseif stamina < 250 then
					stamina = stamina + 1
					Frame.GreenBar:TweenSize(UDim2.new(3.5*stamina/875,0, 0,12), "Out", "Quad", 0.1, true)
				end
			else ChangeSpeed(walk.Value) -- Walk
				if moving and stamina < 250 then
					stamina = stamina + 1
					Frame.GreenBar:TweenSize(UDim2.new(3.5*stamina/875,0, 0,12), "Out", "Quad", 0.1, true)
				elseif not moving and stamina < 250 then
					stamina = stamina + 1
					Frame.GreenBar:TweenSize(UDim2.new(3.5*stamina/875,0, 0,12), "Out", "Quad", 0.1, true)
				elseif moving and stamina >0 then --I added this, but still not working
					tired = true
					
				end
			end
		end
	end
	end

I am dumn to not realized that >0 is supposed to be > 0

elseif moving and stamina < 0 then
tired = true