"9 If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness."
1 John 1:9 NIV
It is then our responsibility to go about our business and do our best to not sin again. That, of course, will never happen until the day we are in heaven. Why? Because we are not perfect...never have been...never will be on this earth. Jesus was the only perfect man to ever walk the earth. We are to strive to be like Him, but the reality of it is we that as long as we walk this earth we will never be perfect like He is. He knows that. But He still wants us to work at it. Working at being like Jesus means we are keeping Him first.
Don't fret when you get knocked upside the head by the world. It happens. But when it does, confess your sins to God and He is faithful and just and will forgive you and cleanse you from unrighteousness!!!
Have a blessed day!