People can’t refrain from talking about the things they are passionate about. Paul says that by knowing the fear of God - a healthy respect for who He is - we persuade men. He says the love of Christ controls us.
When we are passionate about Jesus and His love for us, we won’t be able to stop ourselves from sharing that with others, and through our testimony, they will see God’s glory. If we go day after day, week after week, month after month, year after year, without representing God, we cannot be passionate about Him….