From the Catechism of the Catholic Church:
1776 "Deep within his conscience man discovers a law which he has not laid upon himself but which he must obey. Its voice, ever calling him to love and to do what is good and to avoid evil, sounds in his heart at the right moment....For man has in his heart a law inscribed by God....His conscience is man's most secret core and his sanctuary. There he is alone with God whose voice echoes in his depths."
1783 Conscience must be informed and moral judgment enlightened. A well-formed conscience is upright and truthful. It formulates its judgments according to reason, in conformity with the true good willed by the wisdom of the Creator. The education of conscience is indispensable for human beings who are subjected to negative influences and tempted by sin to prefer their own judgment and to reject authoritative teachings.
1789 Some rules apply in every case:To get the full scope on the conscience and morality you can read the Catechism 1776-1802, but to sum it all up: God often speaks to us through our conscience and we are obliged to follow our conscience, but because we are fallen human beings our decision-making is often clouded from sin, temptation and other harmful things, therefore we must allow our consciences to be well-formed so as to be better able to hear God and make decisions in conformity with His Holy Will and for the true good. This is one of the many reasons that is it good to learn as much as you can about the teachings of the Church, read Scripture, pray, surround yourself with friends also seeking holiness - because all these things will help to form your conscience well so that you can make good decisions, especially if you find yourself faced with a moral dilemma.
- One may never do evil so that good may result from it;
- the Golden Rule: "Whatever you wish that men would do to you, do so to them."
- charity always proceeds by way of respect for one's neighbor and his conscience: "Thus sinning against your brethren and wounding their conscience...you sin against Christ." Therefore "it is right not to...do anything that makes your brother stumble."