Feelings of guilt are a persistent problem for us as Christians. We know two things about sin: 1. it is extremely serious, enough to merit condemnation. 2. We all commit it on a regular basis.
We know three things about sin: 1. it is extremely serious, enough to merit condemnation. 2. We all commit it on a regular basis. 3. Jesus paid for every last bit of it. We have a blessed assurance no other religion offers: There is no condemnation for those who are in Jesus.
So, do you know when you can stop feeling bad about sin? The moment you repent. Now, this obviously doesn't mean you can sin, say sorry, sin, say sorry and continue like that forever. Repentance, by its definition, requires sincerity. But you're going to struggle with sin for the rest of your life. No matter how sincerely you repent, you will soon stumble yet again, and then Jesus sincerely advocates for you (1 John 2:1). Your price is paid, your conviction has been served, you are free.