Have you ever weeded Raspberries only to discover that obnoxious weed growing up with them are Nettles— those horrific stinging plants? This is a survival tactic. Nettles closely resemble the Raspberry leaves, including its texture. By looking like the “wanted” plant, it is more likely to remain and steal nutrients.
In a similar way, evil presents itself as a good, or intermingles with the good, so that it can stay alive in our lives. However, ultimately, it will always seek to choke the good and replace it. For instance, eating is a good; it is something that sustains us. Pleasant tastes are also a good. But when we forget that the purpose of eating is to perpetuate our life, and instead eat or drink for the purpose of experiencing pleasure, then eventually our bodies become accustomed to the doctoring and the over-indulgence of sweets, salt, fat, alcohol, etc.,.— factors in obesity, diabetes, cancer, and other diseases.
Similarly, many actions and intentions of ours are good, but become harmful to us because somehow a false purpose snuck in with it. The Catholic Church calls these actions sins. Original sin—the disobedience of Adam and Eve— was not that they were seeking to be bad, but that they had pursued what they perceived was a good, but in reality, was not. The serpent had dressed up death to be attractive. The consequences of this devastated all of mankind. It's akin to a pregnant woman taking drugs, and through no direct fault of the unborn child, the child will suffer the results of those actions in his own life. Now, if he, himself, say as a teenager, takes drugs by his own volition, all consequences would be his doing. Likewise, when we personally do harm to ourselves, our chosen sins are called “actual” sins— unpleasant consequences that we bring upon ourselves which are not inherited. Actual sins are of two kinds: mortal (fatal—emergency assistance needed) and venial (not immediately devastating, but debilitating over time). The cure for both is reconciliation with God. Acknowledging our sin, and being willing to take the steps necessary to overcome it, is a way to develop the virtue to stay away from it and live a healthy life.
The Sacrament of Reconciliation—which is also known as Confession or Penance— was given to the Church by Jesus Christ when He said to St. Peter: “I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven.” (Matthew 16:18) This command explicitly gives the Apostles the ability to administer sacramental power in order to repair:
“. . . breaches caused by sin. The forgiven penitent is reconciled with himself in his most innermost being, where he regains his innermost truth. He is reconciled with his brethren whom he has in some way offended and wounded. He is reconciled with the Church. He is reconciled with all creation.” (St. Pope John Paul II, RP 31, 5)
“[Reconciliation] doesn’t simply heal the one restored to ecclesial communion, but also has a revitalizing effect on the life of the Church which suffered from the sin of one of her members. Re-established or strengthened in the communion of saints, the sinner is made stronger by the exchange of spiritual goods among all the living members of the Body of Christ, whether still on pilgrimage or already in the heavenly homeland.” (CCC 1469, cf 1 Cor,12:26, cf LG 48-50)