We don't need to understand everything, if we know that God is guiding and directing our steps. Learning to accept living with mystery is an essential part of growing into maturity in our walk with God. When it comes to understanding things, we have our territory and God has His. Our territory only expands when He chooses to reveal things to us. That is why we have to trust Him with all our hearts (Proverbs 3:5-6).
We need to believe the truth of God's Word. His Word is truth and knowing the truth sets us free (John 8:32)! If we are not convinced that God's Word is true, then fear and unbelief come in. That is when Satan has a foothold in our lives. We need to walk by faith and not by sight. We need to trust God's SOVEREIGNTY and the truth of His Word.