Jesus state the certainty of persecution for Christians in this world. The church in Smyrna was encouraged to remain faithful as they endure persecution.
The city of ancient Smyrna (modern-day Izmir, Turkey) was located on the coast and was a harbor City. The church was under the Roman rule and they were not treated well.
the Smyrna believers were spiritually rich which God promised them the crown of life as a reward for their faithfulness.
Revelation capter 2 verse 8-11.
And unto the angel of the church in Smyrna write; These things saith the first and the last, which was dead, and is alive;  I know thy works, and tribulation, and poverty, (but thou art rich) and I know the blasphemy of them which say they are Jews, and are not, but are the synagogue of Satan.  Fear none of those things which thou shalt suffer: behold, the devil shall cast some of you into prison, that ye may be tried; and ye shall have tribulation ten days: be thou faithful unto death, and I will give thee a crown of life.  He that hath an ear, let him hear what the Spirit saith unto the churches; He that overcometh shall not be hurt of the second death.
everyone who will follow Jesus must be prepared for a measure of rejection from the people of the world.
Jesus says blessed are those who are persecuted because of righteousness,
For theirs is the kingdom of heaven.
Are you going through persecution for your faith? Jesus says do not be discouraged hold on and endure to the end as you passed through trials and endure them you become more like Jesus the author and finisher of your faith at the end you will reign with him.
Going through a test is tough coming out of it is rewarding.
Only those who endured to the end shall be saved.