What exactly is a sin of omission? I mean it’s not doing a good work but would it count if it was directed towards ourselves? For instance, after Mass there is a Rosary, but one just decides to leave early because of the reason that they wanted to go home early and saying the Rosary seems like an extra chore would this be a sin of omission or just laziness?
A sin of omission is when a person neglects to act under circumstances in which he can and ought to act, thereby committing a breach of the moral law. It is the neglect of a moral duty.
A sin of omission would be letting an innocent person go to jail because you didn’t speak up with information that you had about the crime.
Many commit sins of omission when they look the other way or “don’t want to get involved” when a child is being harmed-- such as those at Penn State and other institutions including our own Church.
Prayer is a duty we all have toward God. To **never **pray, yes that is a sin of omission. To not want to stay and pray a rosary on a particular day or ever is not a sin at all let alone a sin of omission. We do not have to pray the rosary, it is a private devotion.
Please get help for your scrupulous tendencies. It is quite painful to watch you coming here to question everything in your life day after day.
Firstly, Catholics are not bound to say the rosary. Praying the rosary is not something every Catholic must do on any kind of regular basis. So not participating in a group rosary is not a sin of omission or any other sin.
From Catholic Culture: Sins of omission are against either the law of our creation, or the law of the two precepts of charity, or against the law of liberty. (source)