Acts 9:4-5 "and he fell to the ground and heard a voice saying to him, “Saul, Saul, why are you persecuting Me?” 5 And he said, “Who are You, Lord?” And He said, “I am Jesus whom you are persecuting."
Scripture is very clear that the cross was a one time event, never to be repeated again. When Jesus raised from the dead, He retained His physical earthly body (albeit a glorifed resurrected body). Forty days following His resurrection, Jesus Christ ascended into heaven to sit at the right hand of the Father with Whom He has forever shared the same Divine life (Acts 1:10-11). As Jesus is now in heaven, He ever retains His glorified human body while being ever eternal Deity at the same time (Romans 1:3; 9:4-5). This truth is important, since to be our Mediator (1 Timothy 2:5), Jesus the Son must be very God and very man to represent God to believers and believers before the Father (1 John 2:1-2).
The Key to Understanding What is meant by "the sufferings of Christ" is the union between Himself and Christians
The union of the humanity of Jesus with my own and other Christians is a mysterious but nonethless real union, making us in affect related to Him as adopted brothers and sisters (Romans 8:14-16; Hebrews 2:11-15). The great 17th century Theologian Stephen Charnock explains the significance of Christ's union to us and us to Him:
"He had therefore a nature that could be compassionate towards us and victorious for us. A nature that could empathize with us, and another nature, to render such empathy (to be effective) for our relief. He has the deep feelings of a man to us and the power of God for us. A nature to disarm the devil for us and another nature to be not discouraged by the work of the devil in us and against us. If he had been only God He would not have had the experience of the sense of our misery; if He had only been man, He could not have vanquished our enemies. Had he been only God He could not have died and if He had been only man He could not have conquered death."
Life practical applications of Christ's sufferings and your sufferings
With regards to His Divine nature, the Son executes His Sovereign purposes and ministry to believers not in response to their suffering, but in anticipation of it. As the Person of the Son performs His work as the believer's Eternal High Priest as God, He knows exhaustively what each suffering each Christian is going to undergo - whether it be related to day to day suffering or the ultimate sufferings associated with the Gospel.
I find it amazing how the Son through His Deity, knowing full-well what we will suffer, chooses to enter into the experience of our sufferings by way of His glorified humanity. I am sure if you're anything like me, we would prefer for Jesus to remove difficulties completely from our lives. However, the goal of our Christian walk is to be made like Him in attitude and actions. Suffering is a necessary ingredient in our becoming more like Him. In other words, when we suffer - He suffers, because when He suffered, He did so to provide sufficient grace for our own.
It may be hard for us to wrap our minds around this these truths - however to know that as Christians we are not alone nor separated at any point from Jesus Christ is truly comforting.