The Catholic Encyclopedia describes sins of omission as the following:
“(Latin omittere, to lay aside, to pass away).
“Omission” is here taken to be the failure to do something one can and ought to do. If this happens advertently and freely a sin is committed. Moralists took pains formerly to show that the inaction implied in an omission was quite compatible with a breach of the moral law, for it is not merely because a person here and now does nothing that he offends, but because he neglects to act under circumstances in which he can and ought to act.”

In the book “Where There is Love, There is God”, Blessed Theresa of Calcutta says this regarding sins of omission:

“I want you to pray an examine your conscience [regarding] Sins of omission. Have the courage to say sorry. The best way of saying sorry is to do the opposite action. If you have been moody, be happy…I want you….not to change your place or work but to change your heart. Death can come any time.”

Does this upset you? If so, ask yourself “Why”? The recent “End of the World” prediction which was calculated for May 21st was perhaps not a farce. Perhaps God allowed this predictor to be used as a willing instrument so that we would consider the state of our souls. Perhaps if we were a bit worried or concerned, it is God knocking on the door of our hearts, asking if we are ready to meet Him. If we are not, what would make us feel worthy of gazing upon Him? What good works could you do today? What are you waiting for? You will never regret reaching out. Your only regrets will be what you did not try.