A friend of mine has a saying: "Just tryin' to keep it venial, bro." He'll break out this gem when he's trying to say that his actions might not be perfect, but they aren't that bad. Maybe he used some profanities, but at least he didn't take the Lord's name in vain; or maybe he said something less than charitable to someone, but he didn't tell them to go to Hell or anything; or maybe he bent the truth, but, well, he didn't really lie, per se, did he? It wasn't so bad. He kept it venial.
"Venial" refers to the distinction between venial sin and mortal sin. St. John makes this distinction between sin that is "deadly" and sin that isn't (1 John 5:16), and in the course of time we've come to refer to these two categories as venial and mortal sin. A venial sin wounds your relationship with God, while a mortal sin severs it; that is, while a venial sin hurts you spiritually, it doesn't kill you.
Let's not leap to a false conclusion, though. Let's not be tempted to think, "Well, as long as it doesn't snuff out my spiritual life completely, there's no real harm done, right? So I shouldn't get too worked up about such little sins. I mean, whatever doesn't kill me makes me stronger. It's not so bad. It's no big deal. It's fine. I'm not even going to worry about it."
One day my friend voiced such a notion when he said about something or other, "It's only venial, so it's all good, right?" I responded, "Those do not mean the same thing." (He was joking, but the quotation is illustrative.)
Let's be clear: venial does not equal "okay to do." "Not deadly" does not equal "morally permissible." Venial sin may not break your connection with God, but it's certainly going to weaken it. If you keep weakening it, it will eventually be too feeble to survive. If you take a small branch on a tree and bend it back and forth repeatedly, you will be able to bend it a little more each time, and it will eventually break off. Likewise, when we commit less serious sins, we make it easier for ourselves to push a little further next time, to do something a little more serious. If we don't turn away from that sin, if we keep going in the direction we're headed, we can find ourselves faced with the temptation to commit serious sin, and we'll have made ourselves to weak to resist. Our branch will snap off.
I am not suggesting that we all become super-scrupulous (that's a fun word to say) and run to the confessional in sackcloth and ashes at the slightest of offenses. Prayer and contrition and receiving the Eucharist can help to heal us of these wounds. But let's not fall into complacency and let ourselves begin to slip down the treacherous slope that leads to places we don't want to be. Do try to keep it venial, but don't ignore those spiritual paper cuts. They can get infected.