A wonderful source of depression is unforgiveness. Anxiety and stress are byproducts of unforgiveness, and these are two of the major ingredients of depression and other dark places.
Jesus tells His disciples in Matthew 18: 21 & 22 that they are to forgive those who sin against them seventy-seven times. In the Lord’s prayer He tells us to forgive those who trespass against us. My concordance cites 143 recordings of the word forgive and its derivatives.
I had a client in my depression ministry who was unable to forgive her mother, the aunt who raised her, and three other family members. Even when I asked her why God would forgive her sins if she did not forgive others, she still would not forgive. She rid herself of the worst ravages of depression by electroconvulsive therapy, but a low-level depression remained, and a joyless life.