"Beware lest there be among you a root bearing poisonous and bitter fruit."
In his book, Gospel Coach, Scott Thomas talks about how confession of sin is one of the key ingredients to true repentance. And from Scripture he provides at least seven benefits to confession:
1. Confession of sin gives glory to God. (Joshua 7:9)
2. Confession of sin is a means to humble the soul. (2 Chronicles 26:19)
3. Confession of sin gives release to a troubled heart. (Psalm 51:11-12)
4. Confession of sin purges sin out. (Nehemiah 3:13)
5. Confession of sin endears Christ to the soul that needs atoning. (Romans 7:25)
6. Confession of sin makes way for forgiveness. (2 Samuel 12:13; 1 John 1:9)
7. Confession of sin makes way for mercy. (Proverbs 28:13)
So, what's the point? In your repentance, a key ingredient is confession of your sin, which highly outweighs the benefits of lack of confession and keeping it stored inside yourself.