Prayer and the spiritual life · Question 8
It's already too late for the dead, so what good is praying for them?

The question: “Everything was settled at death, so why do we pray for the dead?”
The Church's answer: Catholics do not teach that a person's fundamental choice is overturned after death. At the same time, we believe that the living and the dead form one communion in Christ, and that we can help one another so that those who died in God's friendship but still need to be fully purified may come to the fullness of joy in God's mercy. So prayer for the dead is not buying God off with money or words in order to reverse a sentence of hell; it is intercession that entrusts the one who has died to the mercy and the purification of Christ. The comfort it gives to those left behind does not by itself prove that it works; it is a practice that flows from the Church's faith in the communion in Christ and in the resurrection.
If they press further: “Does grief that lasts a long time mean weak faith?” — No. Grief can last as long as the love was great. Don't carry it alone; share it with family, a pastor, a counselor. If the despair gets dangerous, ask a trusted adult and a professional service for help immediately.
In one sentence: “We believe that not even death can break the communion in Christ, so we pray, entrusting those who have died to God's mercy.”