Ephesians 6:14
So stand firm and hold your ground, having tightened the wide band of truth (personal integrity, moral courage) around your waist and having put on the breastplate of righteousness (an upright heart).

If we keep the truth of the Word embedded in our hearts, we will not be moved or deceived. Doubt will kill all faith progress, but keeping the mind focused on the truth and trusting in it brings victory. We must have moral courage and integrity to maintain our stance. When a trial comes, we must already know what we believe and judge from that standpoint.