a true believer sometimes suffers anxiety and also those who are not a true believer. Depression is not something that we can escape as humans. Even in the bible, the strong men of God like David and Elijah suffered depression. Elijah at a point was weak and tired and he was crying onto God for help. Being depressed and anxious doesnt mean we lost faith in God, but we are all humans and we can't escape it.
1 Peter 5:7 “Cast all your anxiety on him because he cares for you”
Praying and trusting God is one of the important way to overcome depression and anxiety. We should not hide our pains, but bring them to God who is the healer and problem solver. Praying is a good way for us to communicate with God and tell him how we feel and what is bothering us in the life.
Philippians 4:6 “Do not be anxious about anything, but in everything, by prayer and petition, with thanksgiving, present your requests to God”
Overcoming depression and anxiety is a gradual process which we can't rush. The bible teaches is to always tell God our problems and also surround ourselves with our fellow strong believers. When we feel discouraged in God, he will always strengthen us to believe in him.