We Christians seem to divide rather neatly into two extreme camps when it comes to sin. On one side you have those who seem to feel that as long as they haven't murdered anyone they're okay. Then there is the other group who are convinced that we are all sinners all the time. Today's first reading would be a problem for both. Today St. John tells us,
You know that he was revealed to take away sins, and in him there is no sin. No one who remains in him sins; no one who sins has seen him or known him.
In our creed we can make the audacious claim that the Church is not only one but holy, precisely because the Church is the Body of Christ "and in him there is no sin." St. John raises the bar even higher when he write, "no one who sins has seen him or known him." In other words you cannot simultaneously say, "I know Christ" and "I am a sinner." We have to choose one life or the other. And we have to make that choice on a day to day, sometimes minute to minute basis. The Good News is that when we have steeped outside of Him and sinned we have the Sacrament of Penance as the door to come back inside.
On the positive side St. John tells us, "No one who remains in him sins." . We cannot both remain in him and sin. So when we who say we are Christians sin, we have to first step out of him, step out of the Body of Christ and then we can sin. It is a two step process.
Some Christians act as if sin is inevitable but St. John reminds us that sin is always a choice, two choices really. The first choice is to not "remain in him." The second choice is the actual sin. It seems to me that if we think about the first choice we would sin less often. After all, which of us would directly choose to abandon Christ.
When we face any temptation to any sin we should recall this passage from the First Letter of St. John and ask ourselves whether we want to remain in him or go outside and sin. When we put it that way the choice will be much clearer.