Another way Satan works, is to try to keep you away from the sacraments by making you overly scrupulous. We're not perfect, and sometimes, we'll commit a venial sin, and Satan will prey upon our imperfections, trying to keep us away from the sacraments, by blowing up something we did, or making us second guess ourselves.
In my opinion: Yes, sin is terrible, but making a venial sin in your mind into a mortal one by the influence of the devil, is just as damaging, because your venial sins are taken away right before communion at every Mass, and avoiding the sacraments, to keep you in the state of sanctifying grace, is folly, especially in these times.