Paul wrote these words while in prison. His witness to Christ was crowned with abundant success before the eyes of all throughout the universe. The commission to witness never faded from his mind. We too are to maintain our testimony to Jesus by word and action. We are to witness to Christ as truth, to the Word of God as truth.
Opinion is one thing, truth is another.
Our views, opinions, reasonings, may capture people's interest for a while. But the Christian faith is on a far different footing. The Christian faith, whatever else it is, is not a selfish religion. He who is ready to falter at any moment in the cause of the third angel's message does not know what following Christ means. Witnessing to Christ often seems unacknowledged and unrequited, but it spells loyalty to the divine mission of our Lord and Saviour, and that pays all we need by way of reward.