Some sins have no earthly effects. You could conceivably miss Mass on Sunday for 20 years for example and nothing bad in an earthly sense would happen to you; if you do not have children, family or other close associates who are hurt by your bad example, then nothing bad in an earthly sense would happen to others either.
However, you would be hurting yourself in a spiritual, non-temporal way by distancing yourself from God.
Edited to add, thinking back on my past life especially when young, I think it’s important that people realize there may or may not be any temporal consequences for a sin. Growing up, pretty much every cautionary tale for children, young people, and even some for adults that involved a character committing a wrong act ended up with the character suffering bad earthly consequences as a results of his/ her act. People who stole got caught and punished; people who skipped Mass would have some terrible accident when they went off to have fun, or their parents would find out and be angry with them; people who had illicit sex ended up with an unwed pregnancy, or with an STD, or with their spouse finding out and divorcing them.
The problem is that if you grow up with this mindset, eventually you commit some sin and see that nothing happens in an earthly sense as a result of the sin, and that makes you question everything you learned about sin. Each time you sin and get away with it, it’s a further “proof” that nothing happens and sin is not the big deal it’s cooked up to be. This is how I slid into bigger and bigger sins. When I finally stopped it was because I realized the desire to please God, even though if I committed sin X, Y or Z nothing much was probably going to happen to me in the here and now.