The thought was that a martyr doesn't die out of stubborn, self-determination about what he believes. He is willing to die because of his love for others. His desire to get the message to others is so important that he will not deny that message. If the message and his beliefs were for his own sake, he could avoid physical pain and suffering by keeping his beliefs to himself.
There's a lot to ponder in that thought. Beyond "dying for my sins," why did Jesus die? What am I doing with the good news about Jesus Christ, the Son of God?
Mark 4:10, 14, 22, 24
"the secret of the kingdom of God has been given to you..."
"the farmer sows the word..."
"For whatever is hidden is meant to be disclosed, and whatever is concealed is meant to be brought out into the open"
"Consider carefully what you hear..."
"With the measure you use...
it will be measured to you"
Be careful, that last statement may not be a pleasant experience. With the measure, comes love for others and a strong sense of responsibility. It would be rather foolish to put a fire under a bed (v21).