Life is like a game of chess. You may play your game very well but one wrong decision can cost you. One wrong move can make you lose the game instantly.
As you play the game you cannot see the thoughts of your opponent. As we live we cannot see the devil and his thoughts.
The bible says:
Ephesians 6, 12: For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places. Bible (KJV) https://goo.gl/BNTEmZ
Therefore, it is important to rely on God inorder for us to win. God can see what we cannot see. He also has the power and ability to fight our battles and win.
The same bible also says:
Proverbs 3, 5: Trust in the LORD with all thine heart; and lean not unto thine own understanding. Bible (KJV) https://goo.gl/BNTEmZ
Proverbs 3, 6: In all thy ways acknowledge him, and he shall direct thy paths. Bible (KJV) https://goo.gl/BNTEmZ
Proverbs 3, 7: Be not wise in thine own eyes: fear the LORD, and depart from evil. Bible (KJV) https://goo.gl/BNTEmZ
Proverbs 3, 13: Happy is the man that findeth wisdom, and the man that getteth understanding. Bible (KJV) https://goo.gl/BNTEmZ
Proverbs 3, 14: For the merchandise of it is better than the merchandise of silver, and the gain thereof than fine gold. Bible (KJV) https://goo.gl/BNTEmZ