"God does not save those who are only imaginary sinners. Be a sinner, and let your sins be strong (sin boldly), but let your trust in Christ be stronger (believe much more boldly), and rejoice in Christ who is the victor over sin, death, and the world."~ Martin Luther
This is not an invitation to license.
This is an invitation to be who you are, a sinner saved by grace through faith in Jesus alone.
This is for the moments of failure and folly when you feel like you can't be a Christian, when you are such a disappoint to yourself and others.
Embrace the FACT that you are a sinner in that moment and find comfort in the FACT that Jesus did not come to save hypothetical sinners, but real, tangible, dirty, rotten sinners like you and me.
Sin boldly and believe even more boldly that Jesus knows you are a sinner and has spent Himself to save sinful little you.