Acts 20:24 (NKJV)
In the USA during the 1920s and 1903s there was a law enforcement agent named Eliot Ness. Eliot Ness was involved in the work of bringing an end to the career of the gangster Al Capone. Eliot Ness and the group of men he worked with were known as "The Untouchables" because they refused any attempts to bribe them by people like Al Capone. At a time when corruption and bribery of government officials was rampant, Eliot Ness and his men ignored those who tried to get them to stop their work and they were ultimately able to help stop Al Capone and his criminal activities.
It has been said that everyone has a price, that everyone can be bribed or coerced into not doing what should be done. Eliot Ness and his men were called The Untouchables because this was not true about them, no matter what others tried to do they would not be stopped. During his lifetime, Paul was also "untouchable" in that nothing mattered to him except doing the will of God. For Paul, his goal and ambition in life was to serve God and no matter what others did or what happened in his life it did not alter his course; nothing could stop Paul, he was untouchable.
How could Paul ignore the opposition he faced and the difficulties he endured to continue in his ministry and say that not even his life mattered to him as much as doing the will of God? The answer is that Paul's main focus in life was the will of God. None of the things that happened to Paul or anything others tried to do to stop him moved him, none of those things could touch him. God has a purpose for our lives as much as He did for Paul. Are we "untouchable", or are there things that we have allowed to hinder us from fully serving God? As we continue to focus on God and His will it will help us to stay on the course that God has given to us.