Well , that's good question to ask , that's true the support after break up become a resistance and the opposite and that's for a reason that price which was support and all traders want buy from it and they do that already but when it break down for some reason and the price continue going down the traders wait until to get their money back and the price come back up again and get their money and when they get back their money they start to sell what they bought before so the price come down again and that zone become a resistance.