He does not know God's plan or how it works, and he does not know how he fits into God's plan. Darkness brings about a failure to orient to the grace of God. The result is arrogance and legalism, lack of forgiveness, lack of graciousness. Darkness causes inner misery, unhappiness, lack of peace. These things cannot be compensated for by anything in life, but the negative Christian spends his life in a frantic but futile pursuit of happiness through the details of life.
Darkness can bring about neuroses and psychoses - anxiety.
Be anxious for nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God. Darkness results in a frantic search for happiness through details of life, or through some form of sublimation. Darkness leads to slavery to the details of life. Darkness leads to apostasy, erroneous thinking, false doctrine in the soul. Darkness is accompanied by a lack of capacity to love, leading to pseudo-love towards God, family, the community.