The Word says to fear God:
Mat 10:28 And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell.
We are God's children and as we press into His presence we know peace and rest. God is love and perfect love casts out all fear.
satan was indeed foolish to think he could sit on the throne of the most high but even then we are not to disrespect him:
Jud 1:9 Yet Michael the archangel, when contending with the devil he disputed about the body of Moses, durst not bring against him a railing accusation, but said, The Lord rebuke thee.
We are told that we have authority over the powers of darkness in the Name of Jesus but that is kind of like a loaded gun- it is only effective if used properly. We move only at the Spirit's lead- Like Jesus we move only at the Father's biding in the power of the Spirit.