For any thought you want to eliminate, there are two ways of doing it. Either you manifest it, or you put it in your meditation. If it stays in your subconscious mind, it will become a block there. It will recur; it will haunt you. When you block something, the more you block it, the more powerful it will become. So it is basically very dangerous. But the haunting past can be burned away forever through meditation. When you are chanting and meditating and negative thoughts start coming, let the thoughts come, but also let your mantra go on. You will be relieved of that negative thought forever. It is the most positive way of doing it.