Question:
But do we have to confess all our sins?

Answer:
Is it possible to confess all our sins? Could you remember them all? Of course not.

Sometimes we sin and don’t realize it, but God forgives us because Christ bore every one of “our sins in His own body on the tree” (1 Peter 2:24), and “Christ died for our sins” (1 Corinthians 15:3). He forgives even our future sins, because every one of our sins were future when Christ died.