When Peter came to the end of writing the second book which bears his name, he gave some very practical advice.  He ended by saying, "Be on your guard so that you may not be carried away by the error of lawless men…" and "grow in the grace and knowledge of our Lord and Savior Jesus Christ."  Notice the two words: guard and grow.  That was the practical advice of a fisherman who knew that he had to defend his fishing grounds, but he couldn't spend all of his time keeping others out of what he felt belonged to him.  He had to fish.  He had to grow.