The truth about sin and righteousness

I’ve struggled with this terribly lately. Sin is crouching at my door constantly. 

If we are to judge others based on the fruit of their lives, how do we know when sin is present who’s in what camp? 

I ache to have the assurance of faith and to see the assurance of faith in others. What about fringe issues, things like alcohol, swearing, modesty? I hesitate to even bring these up, it’s just that there are people in my life that practice things that appear contrary to my understanding of righteousness. 

If we are born again, we can’t continue in sin. We will practice righteousness. If we love Jesus we will act like him! Big what about when we don’t? What about resetting sins that trip us up over and over again?

My understanding is this— Jesus is my righteousness, I’ll never be perfect. I’ll never be enough, even on my best day. But I must practice righteousness if I am born again, turning away from sin and acts of unrighteousness. 

So what is sin, anyway??