Repentance is simply a change of mind that leads to a change of action. When we sin as Christians, the Holy Spirit convicts us. If you're a new believer, you may have wondered why you feel so bad about things you never thought twice about. The answer is simple: The Holy Spirit is convicting you. He's challenging you to growth through repentance. 

When we are convicted by the Holy Spirit, it is then our response to repent. We are all messed up to one extent or another. We all fall short. And thank God that Jesus will meet you WHEREVER you are! BUT Jesus doesn't want you to stay WHERE you are. He wants you to grow.

That growth happens through being convicted and repenting. 

Ask the Lord to reveal anything you haven't repented of in your life, and ask him to restore to you the joy of your salvation like David did in Psalm 51:12: 

12 Restore to me the joy of your salvation,
    and make me willing to obey you. Psalm 51:12