It is not just a physical thing, but rather it is spiritual. Sorrow is often embedded in the past events in our lives—our losses, regrets, failures and so on. When our desires are fixed on the past, we will have constant sorrow because we cannot regain, change and correct the past. We can only act on the future. Sorrow has its place, but we must not allow it to dictate our lives. We have to learn to live with it, but to live strongly.
Paul had much to regret in his attempt to destroy the Church that was the Body of Christ. He remembered the stoning of Stephen and others with deep regret. Paul also realized that he could not dwell in the past—he needed to look to the future if his life was to have value (Philippians 3:13-14). Forgiveness of sin and a connection with God comes at the beginning of conversion. The blood of Christ makes our relationship with God possible. His blood covers our past and opens the door to the future. Look forward to that future and away from the past.