I woke up on a Saturday and almost immediately starting thinking about the bad day I had at work the day before, and the mess I was headed back to on Monday. Then I remembered the old saying: "Leave your work at the office." It's a reminder to not let the stress of the office rob you of the well deserved joy you should have when you return home. Your job pays you to worry 9-5 during the week, but you don't owe them your peace outside of those hours.
Unfortunately, many of us have a similar problem when we become Christians, bringing the guilt and shame of our already forgiven sins "home" with us into our new life in Christ. Despite the fact that Jesus has separated our sins as far as the east is from the west, we still think they're hanging over us, dimming the smile on God's face when He looks at us.
Today's good news is that those sins are really and truly gone! "I, I alone, am the one who wipes out your wrongdoings for My own sake, And I will not remember your sins." (Isa 43:25 NASB, emphasis mine.) Jesus didn't go to the cross so you could have an uncomfortable, awkward relationship with your God; He went there to perfectly repair the broken. You may approach your God like an innocent child, and you can fully expect him to keep His promise to not remember our sins.
But maybe you do have some unconfessed sin left in your heart. When we sin in our Christian life, it doesn't rob us of our salvation, but it can "grieve the Holy Spirit", casting a shadow over the place where we could be standing in the fullness of His light. The good news is that God wants to quickly and completely move past your sin; all you have to do is confess it. The momentary guilt you feel about what you've done is God's way of getting you to lay it at the cross and be done with it. So confess your sins quickly, and watch God permanently erase them with His permanent love!