In the 1st reading from 1 Corinthians 8 at morning Mass, Paul wrote: "If food causes my brother to sin, I will never eat meat again, so that I may not cause my brother to sin." Paul is saying that even what you do is not a sin per se, it becomes sinful if it wounds others' consciences when they copy you. In most cases, what we do is sinful, and if that causes others to sin also, we have committed a much more serious sin. A common example would be parents who behave badly causing their children to behave in a similar way. It is basically keeping others away from God!