When we trust God and his promises we can overcome doubts and anxities easily. The Bible teaches us to pray, read God's Word, and remember His faithfulness in our lives.
Philippians 4:6-7 says, "Do not be anxious about anything, but in every situation, by prayer and petition, with thanksgiving, present your requests to God."
When we rely on God instead of our fears, He gives us peace that guards our hearts and minds.
If we continue to obey God commandments that is how our faith in Him will continue to grow rapidly. Even when we do not understand everything, we can choose to trust His wisdom and timing. By surrounding ourselves with fellow believers, meditating on Scripture, and keeping our focus on Christ, our doubts become weaker and our confidence in God becomes stronger.