When viewing an image of Christ crucified, the physical sufferings of Christ are evident. He is typically portrayed in agony. His body physically distorted. His wounds gruesomely depicted in great detail. Commentaries have described the brutality of His crucifixion in great detail. The image of Christ crucified and commentaries assist in meditating on His great sacrifice.
In addition to His physical sufferings, Christ suffered mental anguish, as seem in His prayer on the Mount of Olives. Judas Iscariot has betrayed Him, and His remaining disciples are beginning to abandon Him, for they cannot remain awake to pray with Him.
When I meditate upon Christ crucified, I meditate upon the mental anguish He suffered. This is how I unite myself with His sufferings. I unite the pain I have endured from betrayal and abandonment by loves ones who I loved and trusted. Such betrayal and abandonment pierces the heart, chills the marrow, and mortifies the spirit.
When I envision Christ crucified, I envision Him looking down from the cross. Of the twelve, He sees only John. The other eleven who He shared the three years of His ministry with, who swore their allegiance to Him, who He had placed His trust in, are nowhere to be seen. The betrayal and abandonment by His disciples must have pained Him as much as the nails that pierced His hands and feet.
The pain Christ bore on the cross was the pain of sin. I see my sin as betrayal of Christ, an abandonment of Him. This is also how I see the eternal agony I will endure, if I do not repent from my sin. My sinful abandonment of Christ separates me from him. This is when I call upon him, ask for forgiveness in His great sacrament of reconciliation, and enjoy the great joy of His mercy and returning to Him.