what does the bible say?
Sin is anything that is opposed to God. It is rebellion against God's rule and results in spiritual separation from Him. Because God is life, the result of sin is lack of life - both physically and spiritually. Because of Adam’s rebellion in the garden (Genesis 3:6), everyone on earth is born separated from God and faces the consequences of sin. Without Jesus, sin results in eternal death. However, sin has consequences beyond an eternity in hell.
During this life, sin leads to bad choices resulting in broken relationships, unfulfilled promises, and addictions to things that cannot ultimately satisfy us. Even for a believer, sin results in symptoms of spiritual death. When we sin, we experience a break in our relationship with God. As a result, we may experience confusion, loneliness, guilt, purposelessness, or the like. This is what spiritual death feels like. For believers, this is not a permanent state, but it is a consequence of unconfessed sin.