Jesus said in the world you shall have tribulation but be of good cheer I have overcome the world. This is written in John 16:33.
Let us ask why Jesus said these. According to the Bible , all have sinned and fall short of the glory of God. And the wages of sin is death. But in John 3:16 it is written God so loved the world that He gave His only begotten Son that whosoever believe in Him (Jesus) shall not perish but have everlasting life.
The world as of now is still reaping the consequence of man's sin as orchestrated or tempted by Satan. But man's sin is already dealt its match by the sacrifice and death of Jesus Christ. Jesus experienced death for sinners who will believe in Him. Our sins has been paid for if we believe in Jesus Christ. No one else qualified to die for our sins. Jesus lived a sinless life, fully pleasing His Father, and on Him was placed the iniquity or sins of us all. By dying for our sins Jesus has overcame the world. And because of that we have or will inherit eternal life.
God gives us His Holy Spirit as a seal or deposit of that promise.
You may ask , why do we still suffer today, why do we still die ? I believe God is still waiting for others to repent and turn to Him. There are still others who have their sins unpaid by the blood of Jesus Christ. Why unpaid ? because they have not believed in God's Son Jesus.
Meanwhile those who believe in Jesus and are still on earth are supposed to tell the world that Jesus saves and He is coming back.