God knoweth that ye are His own. Wrestle, fight, go forward, watch, fear, believe, pray; and then ye have the infallible symptoms of one of the elect of Christ within you.
In the arena
Proof that you belong to God is action, but God doesn't need that proof. He already knows. The proof is for you, so you don't lose heart. Before bed tonight, get on your knees and pray out loud. Pray for your family by name. Confess one specific sin from today. Lament the sin, then ask God for strength to overcome it tomorrow. Ask God to equip you to wrestle and fight.
Read Ephesians 6:10-18, for if you are going to wrestle and fight, you'd better put on some armor. And the point of this armor? To keep alert (watch) with all perseverance, and to make supplication for all the saints (v.18). Prayer both puts you in the fight and equips you for other fights to come.