The Bible is extremely practical in how we may live out our faith. There are many warnings from the lips of Jesus as he walked on earth - here are three.
Matthew 16.6: Be careful, Jesus said to them, Be on your guard against the yeast of the Pharisees and Sadducees. There is false teaching that needs to be avoided otherwise, like yeast, it will penetrate the entire body. If we are to live faithful lives for Christ, if we are to be his faithful followers, we must be careful, be on our guard against false teachings.
Matthew 26.40-41: Then he returned to his disciples and found them sleeping. Could you men not watch with me for one hour? he asked Peter. Watch and pray so that you will not fall into temptation. The spirit is willing but the body is weak. Thank God that he knows our weaknesses, but that does not take away from watching and praying. I think there is a special warning here when our bodies are weak - tired, depressed, suffering in some way. We need to watch that we do not fall into temptation like Peter would later on and deny that he ever knew Jesus. Sin is a denial of our relationship with God and we need to guard against tempation.
Luke 12.15: Then he said to them: Watch out! Be on your guard against all kinds of greed; a man's life does not consist in the abundance of his possessions. How necessary to hear this warning from Jesus. We need to watch out and be on guard against taking the good things in creation and making them gods we worship. Yes, in our society we call them misplaced priorities but the Bible calls it greed - a sin.
This is a sampling to show that part of our walk will be to stand guard against sin - watch out, be careful, stand firm, be immovable - that is part of the calling of a believer.