Yes, there is a secret. secrets are things that are unknown. Jesus said resist the devil and he will flee from you. He did not say he would come back. The reason he comes back in some people 's life is because he have succeeded in tempting you in certain things. he is just working in your weaker areas . In order not to fall into temptation, you must endure temptation from the devil. If he cannot succeed anymore in what it is he is tempting you to do, then He will know that he have been defeated and will flee. But you must overcome each temptation, not giving in to any. Just one will keep him coming back.. This goes for me and every other believer as well. This is what Jesus meant by resist him, never giving in as he did not give in. and he will surely leave.