Do you remember the story in Matthew 9 about the boy who had a deaf & dumb spirit in him, and the disciples could not cast it out. So when Jesus, came, and inquired as to what was going on, the father of the son told him, that the disciples could not cast out the spirit from his son. Jesus answered with, "Oh faithless generation, how long shall I be with you, how long shall I bear with you?" Then He asked the father how long had he had the spirit, what does it do, and then commanded the spirit to come out. Before that, the father told Jesus, "If you can do anything, have compassion on us", Jesus told the father "if he could only believe, the father cried out, "Lord I believe, help my unbelief."
You see I don't believe the father of the boy believed in the power Jesus had given to the disciples. Therefore, his faith would not allow his son to be healed. But then when Jesus came, he still asked Him, "IF" He could do anything, he still lacked faith, but he asked Jesus to help his unbelief in that area.
Later when the disciples were alone with Jesus, they asked why they could not cast out the spirit. Jesus told them that this kind of spirit can only come out by prayer and fasting. What does prayer and fasting have to do with it, you might ask? It brings focus on the power of GOD working through you. When you pray and fast, you empty yourself of everything, and focus only on GOD. You fill yourself up with the the power of GOD .
Sometimes, the spirits stay in a person, because the host, the person they occupy, does not want them to leave. They are comfortable in the way they behave. They are lost and do not know any better. That is when you have to pray and fast for the person, that they will accept the Lord, and then pray the sprit out of them. When you pray evil spirits out of one, they will find another home. That is why Jesus sent them into the swine, and then they ran into the lake and drowned.
Mark 9 v 21-24.....So He asked his father, "How long has this been happening to him?" And he said, "From childhood. And often he has thrown him both into the fire and into the water to destroy him. But if You can do anything, have compassion on us and help us." Jesus said to him, "IF you can believe, all things are possible to him who believes." Immediately the father of the child cried out and said with tears, "Lord I do believe; help my unbelief!"......
Mark 9 v 28-29....And when He had come into the house, HIs disciples asked Him privately, "Why could we not cast it out?" So He said to them, "This kind can come out by nothing but prayer and fasting.".....
You see all it takes on our part is to believe. And when you are praying for something that takes the power of GOD to accomplish, remember to pray and fast, so as to empty yourself, and fill up on His power, and not your own.