You became a child of God once you identified with Christ and His victory over the enemy. John describes this by saying, "you are from God" - 1 Jn 4:4. He goes on to say in this scripture that you have overcome the enemy and his agents because as a child of God you have the Holy Spirit living in the inside of you.
The fact that you have God Spirit's on your inside means that you already have the capacity to overcome in any situation. However you must learn how to engage the Holy Spirit. This starts by acknowledging His presence and power. Then you must develop a relationship and stay in fellowship with Him. So that when you face those situations you are conscious of His presence and His promptings.
In order to develop a relationship and stay in fellowship with God's Spirit you must spend time in God's presence during your prayer, mediation and thanksgiving time. As you spend time in God's presence learn to be sensitive to His voice and direction. As you follow His direction in every area of your life you will walk in total victory.