This question comes from The Heidelberg Catechism. It is question Question # 1. It strikes me that this first question, gets right into the truth that enabled the apostles to rejoice in all of the up and downs of life. Here, in the form of a catechism question for children, is the gospel in which Paul finds his strength and serenity in Romans 8.

Question 1. What is your only comfort in life and death?

Answer: That I with body and soul, both in life and death, am not my own, but belong unto my faithful Saviour Jesus Christ; who, with his precious blood, has fully satisfied for all my sins, and delivered me from all the power of the devil; and so preserves me that without the will of my heavenly Father, not a hair can fall from my head; yea, that all things must be subservient to my salvation, and therefore, by his Holy Spirit, He also assures me of eternal life, and makes me sincerely willing and ready, henceforth, to live unto him.