I, John, both your brother and companion in the tribulation and kingdom and patience of Jesus Christ, was on the island that is called Patmos for the word of God and for the testimony of Jesus Christ. Revelation 1:9
The apostle John identifies with believers who are suffering at this time under the rule of emperor Domitian. This book was most likely written around 90 AD. Believers faced incredible persecution and John himself was exiled to the island of Patmos for his testimony for Jesus Christ.
We must remember how intimately John walked with Jesus when He was upon the earth. John referred to himself as the disciple who Jesus loved, not elevating himself above the other apostles, but understand how much love Jesus had for him.
John also took carry of Mary once Jesus left the earth and Jesus commanded him to do this from the cross. John was part of Jesus inner circle with James and Peter.
John walked closely with the Lord and was willing to suffer for the name of Jesus. He was given the vision of Revelation because the Lord knew he would be faithful to write it down and be obedient. When you come to know the depths of the Lord's love for us and all He accomplished for us, you are willing to suffer for the Kingdom.