It is possible for us to use the Power in His Name to cast out devils, to prophecy, yet it does not mean that we are walking in His path for us, donig what you think will impress God may just be doing something totally different from what God wants you to do.
When we try to impress God, or when we think we are doing God’s will we actually are trying to do what we think is good, what God wants. This shows that we do not really know our God, or even worse, not at all. So the cause of sin can come from doing the desires of the flesh, and also trying to fullfil the desires of the flesh to imrpess God.
sin comes from the body, but the flesh can defile the soul and the spirit, and when the 3 of them is defiled, what can we do, there is no more good left in us to let us have good conscience.
We need to know our God, read the Bible, it is the only book that document His existance that is truly written by the people that know Him best and became a witness to all nations. It is filled with prophecy, teaching and stories to make us know God even more, what is He like, what does He like, and how to make our own personal relationship with Him.
Then we know what He wants us to do, not only are we avoiding the wickedness of the flesh, but also the arogance of the soul. He will give us a new heart and we will serve Him with a soft heart that seek no applause, but work good for cause.