He who has an ear, let him hear what the Spirit says to the churches. To him who overcomes I will give to eat from the tree of life, which is in the midst of the Paradise of God. Revelation 2:7 (NKJV)
Although Jesus has conquered Satan and his hosts, they are not yet confined to their final destiny—the lake of fire. In his book The Cross of Christ, author John R. W. Stott explains the tension in this manner.
For though the devil has been defeated, he has not yet conceded defeat. Although he has been overthrown, he has not yet been eliminated. In fact, he continues to wield great power.
On the one hand we are alive, seated and reigning with Christ, with even the principalities and powers of evil placed by God under His (and therefore our) feet; on the other hand we are warned that these same spiritual forces have set themselves in opposition to us so that we have no hope of standing against them unless we are strong in the Lord’s strength and clad in His armor.
The tension is part of the Christian dilemma between the “already” and the “not yet.” Already the kingdom of God has been inaugurated and is advancing; not yet has it been consummated.
Place your faith in the finished work of Christ on the cross, and you will always be led in His triumph.