Jesus said to St. Faustina........ and so we should pray
"'My daughter, help Me to save a certain dying sinner. Say the chaplet that I have taught you for him.' When I began to say the chaplet, I saw the man dying in the midst of terrible torment and struggle. His Guardian Angel was defending him, but he was, as it were, powerless against the enormity of the soul's misery. A multitude of devils was waiting for the soul. But while I was saying the chaplet, I saw Jesus just as He is depicted in the image. The rays which issued from Jesus' Heart enveloped the sick man, and the powers of darkness fled in panic. The sick man peacefully breathed his last. When I came to myself, I understood how very important the chaplet was for the dying. It appeases the anger of God." (Diary, 1565).
Devotion to the souls in Purgatory contains in itself all the works of mercy, which supernaturalized by a spirit of faith, should merit us Heaven. de Sales