Also keep Your servant back from presumptuous sins. Let them not rule over me;
Then I will be innocent, And I will be blameless of great wrongdoing- Psalm 19:13 NASB 

For most of us, our biggest fears besides spiders, snakes and germs are:

Fear of being judged. 

Fear of social shame or humiliation. 

Fear of the future. 

Fear we will not get our needs met. 

With all due respect to everyone’s fears, these are all the wrong things to be afraid of. The short-list of things the Bible says we ought to fear are: 

God (Ecclesiastes 5:1-2, Matthew 10:26, 2^nd Corinthians 7:1, 1^st Peter 2:17). 

Missing out on the grace of God (Hebrews 12:17, 1^st Peter 5:5). 

Getting tangled up in some sort of sin (Hebrews 12:1). 

And:

The obstinate refusal to fully repent of a known sin (Jude 1:4, Psalm 19:13, Hebrews 10:26). 

There are all sorts of reasons why Christians choose not to repent. But, truth-be-told almost all of them go back to the list of all the wrong things to be afraid of. Folks resist repentance because admitting wrong (a crucial aspect of repentance) might lead to social shame or change how people see us. Sometimes we fear the confession that might need to go along with our repentance will affect our future or keep us from getting our needs met.  

So. 

 None of the above concerns are entirely irrational. Those are real issues. Sometimes there are consequences for coming clean and getting things right with God and people.  But we have to remember that all Christians sin.  Most Christians sin mostly on accident, a few sin on purpose but all Christians sin (1^st John 1:8-9). There is grace for sin (Romans 3:24), but only when we choose to do things God’s way and repent. Choosing not to repent is effectively choosing misery. It will not result in a loss of salvation but it will create all sorts of other painful problems with unintended consequences, including:

We open ourselves up to all sorts of other sins- 

This is a real thing. Anytime we sin and refuse to acknowledge the sin, feel remorse for it and turn away from it our conscience becomes seared (1^st Timothy 4:1-3). The human conscience is an oddly delicate thing. Once it is seared it becomes much less prone to feeling conviction and sinning feels like a lot less of a problem. This is why when a Christian is outed for some form of moral failure there is almost always a long list of their sins. They lied AND they cheated on their spouse AND they used drugs, AND they stole money AND they treated people like garbage. Nevertheless, the whole ugly muddle always begins with the very first sin they refused to deal with God’s way (Acts 3:19, Matthew 3:8, Romans 2:4)

We run the risk of making ourselves sick- 

Again, this is a real thing.  If someone is a genuine Christian refusing to repent always leads to feelings of guilt and even self-loathing (Psalm 32:3). Because there is a connection between our minds, hearts and bodies eventually those feelings of guilt and self-loathing create stress that damages our physical bodies. (Proverbs 13:12, Proverbs 14:30, Acts 2:26).  Symptoms of stress eventually affect every part of our bodies. 

It becomes very difficult to us to do ministry and life well–  

All Christians receive the Holy Spirit when they put their faith and trust in Jesus (John 14:16-17, Acts 2:38, Romans 15:16, Ephesians 1:13). Nonetheless, believers in Jesus are also told to be filled with the Holy Spirit (Acts 9:17). A continual filling of the Holy Spirit brings joy, peace, wisdom and insight which empowers us to do ministry and life well (Acts 4:31, Acts 13:8-10, Acts 13:52).  It is possible to grieve the Holy Spirit. We grieve the Holy Spirit anytime we live in a way that runs counter to the biblical truths we have been taught (Isaiah 59:1-2, Isaiah 63:10, Ephesians 4:30). Anytime we refuse to repent we forfeit the spiritual power and sense of peace that comes with having the Holy Spirit operating in our lives at full capacity. The net effect of this foolishness is we do life and ministry in our own feeble strength and power (Philippians 4:13).  This never leads to anything good or life-giving. 

Intimacy with God is broken-

Sin has caused human beings to run and hide from God (metaphorically speaking) since the fall of mankind. This inclination is literally part of our human DNA (Genesis 3:8-10, Romans 5:12). We hide from God because we understand intuitively sin breaks intimacy with God. This dynamic creates all sorts of problems and unintended consequences in our lives. The worst being that we no longer feel we can run to God for help with the problems caused by our sinful choices. The answer is always just give it up and repent already (Acts 3:19). 

Most of the time we hang onto sinful junk because we really want to maintain complete control of any consequences we might suffer. Control always comes at a high price in this life. God graciously gives us the abundant, joyful life Jesus promised when we make a practice of confessing our sin and repenting quickly (John 10:10). Choosing repentance always leads to peace, intimacy with God, a clean conscience and the ability to operate at maximum spiritual capacity. All of those blessings are worth giving up anything we have to give up.