Why can't there be two loops on one script?

I created some code and it was in a value, in side of the value there was a script and here's what it said.

    while true do
wait(1)
    if script.Parent.Value >0 then 
        script.Parent.Value = script.Parent.Value -1 -- This script removes 1 value if the value is more than 0
end
    end



-- next while true do

    while true do
wait()
    if game.Workspace.Part.Anchored == true then
        script.Parent.Value = 0
end

Now the one above runs but the one below doesn't.... Is there a limit to one while loop a script?