Worshiping God is never dependent on whether we are worthy to enter His presence or not because if it was we'd all be disqualified. It is rather an acknowledgment of what Jesus has done for us so that we are now free to enter His presence.
Have you ever tried singing to God during corporate or personal worship time and felt that you were too sinful to experience the move of the Holy Spirit? If you have then welcome to the club. Many believers struggle with feeling too "dirty" to worship God even though they view themselves to be Christians.
God's presence is the pinnacle experience for all believers. It is what we must all aspire to have everyday. As Psalm 84:10 says, "For a day in your courts is better than a thousand elsewhere. I would rather be a doorkeeper in the house of my God than dwell in the tents of wickedness."
But how can we enter the presence of a holy and blameless God who cannot stand the presence of sin when we cannot stay pure and sanctified for more than a day?
The power of sin
As believers, we are often tricked by the enemy to think that sin is not a big deal. While God's love is bigger than our sin, that does not mean that sin is insignificant. Sin is powerful and can bring curses and even death (Romans 6:23). When we struggle with sin, we give the enemy a foothold to condemn us into thinking that we aren't good enough to enter God's presence.
Condemnation is one of the top arsenals in Satan's weaponry and he's ready to use it anytime. That's why the psalmist David once said in Psalm 51:2-3, "Wash me thoroughly from mine iniquity, and cleanse me from my sin. For I acknowledge my transgressions: and my sin is ever before me." We need to be cleansed of sin to be rid of condemnation so that we can enter God's presence without blemish or blame.
How we are made righteous
But to know that we need to be spotless is only the beginning of guilt-free worship. The bigger question is "How can I sanctify myself so that I can enter God's presence?" The answer -- sadly, there's nothing we can do. By our own strength, we will never be able to enter God's presence. We are just too sinful and too imperfect to enter the courts of God.
However, even when we cannot find our own way to God, He makes a way for us. That's why the Father sent Jesus to die on the cross as atonement for our sin so that we would once and for all be free from the consequence and clutch of sin in our lives. Jesus has become our atoning sacrifice, the great High Priest that paves the way for us to enter His holy of holies (Hebrews 4:14-16).
When God tore the veil that moment that Jesus died on the cross, He gave us the assurance that now our sin has no hold over us and that we can freely worship Him and come to Him if we believe that Jesus is more than enough to make us holy and righteous before His sight.
