A certain holy monk was taken in a dream by his guardian angel and shown a vast plain covered with many cities and men. On one side of the plain, a rushing spring of water came forth from a hillside and divided into seven clear streams, which flowed down into the plain. At the other side of the plain, another fountain rushed up from a dark cave and also spread out into seven streams.
He watched the streams that came from the cave and saw many people drinking eagerly from their waters, which were sweet to taste. Soon after drinking the water, though, these people were seized with violent pains and vomiting, and many died.
"That is the plain of self-will," said the angel. "And its seven poisonous streams are the seven deadly sins. Now, look across the plain to where the seven rivers of life take their rise from the hill of Calvary."
The seven rivers of life were not so sweet to the taste, but they had great powers. The sick who drank from them were healed, the old were made young again, the ugly became beautiful and, in some of the rivers, the dead were brought back to life.
The seven poisonous rivers are the seven capital sins: pride, avarice, lust, envy, gluttony, anger and sloth. The seven rivers coming from Calvary are the sacraments: baptism, confirmation, the Holy Eucharist, penance (confession), anointing of the sick, Holy Orders and holy matrimony.
Paragraph 1084 of the Catechism of the Catholic Church explains, "The sacraments are perceptible signs (words and actions) accessible to our human nature. By the action of Christ and the power of the Holy Spirit, they make present efficaciously the grace they signify."
All seven sacraments were instituted by Christ, and all can have their basis demonstrated in Sacred Scripture. Most of us take them for granted. But the sacraments are the very life-giving blood flow of the Church. Without the sacraments, we'd all be doomed. They're as important to our spiritual and eternal life as air, food and water are to physical life.
All of the sacraments either give or increase sanctifying grace, depending on the sacrament and the state of one's soul at the time of reception. Sanctifying grace is best described as "God's life in us." In other words, one can't get to Heaven without sanctifying grace. If one dies with the absence of sanctifying grace in the soul, one goes to an eternity in Hell. Sanctifying grace can't be acquired after death in Purgatory because there are no second chances after death, and death never announces itself before it comes.
Being in possession of sanctifying grace is to be in what's called a "state of grace." Not having sanctifying grace is to be in a state of mortal sin. Being in a state of grace is absolutely necessary in order to receive confirmation, the Holy Eucharist, Holy Orders and matrimony. A state of grace is ordinarily necessary for the anointing of the sick, if the recipient is conscious. Not being in a state of grace when receiving these sacraments is sacrilege — a mortal sin that places that person in jeopardy of Hell.
The sacraments are grouped into three separate categories: the sacraments of initiation, reconciliation and vocation.
The sacraments of initiation are baptism, confirmation and the Holy Eucharist. They're called sacraments of initiation because these are the sacraments through which we begin the Christian life.
The sacraments of reconciliation are penance and the anointing of the sick. They're called sacraments of reconciliation because they reconcile us to God. The primary work of the anointing of the sick is to bring spiritual healing to the soul and sometimes also the natural healing of the body.
The sacraments of vocation are Holy Orders and holy matrimony. They're vocational sacraments because the priestly state and the married state are lifelong vocational commitments.
Some of the sacraments — baptism, confirmation and Holy Orders — can only be received once because they place an indelible mark (called a character) on the soul. This character is visible to God, His angels and saints in Heaven, and to the demons. Indeed, the mark of Christ mentioned in Revelation is the character on the soul from these sacraments, as opposed to the mark of the Beast mentioned in the same book.
There are two elements necessary to constitute a true sacrament: matter and form.
"Matter" is some sensible, concrete thing or action. Examples would be the water in baptism or the bread and wine used when confecting the Holy Eucharist. "Form" refers to the essential words used by the minister of the sacrament. Examples here would be "this is My Body" in the Holy Eucharist or "I absolve you from your sins" in the sacrament of penance. Both the matter and form must be used at the same time and by the same minister to produce a valid sacrament.
The minister of the sacrament is a person who has received from Jesus the authority to act for Him in giving that particular sacrament. The ordinary minister of a sacrament is usually a priest (which includes a bishop). Sometimes, the ordinary minister can be a deacon. In Holy Orders, the ordinary minister is always and only a bishop. In the case of matrimony, the ordinary ministers, believe it or not, are the bride and groom. There can be an extraordinary minister in the case of baptism, but only under (you guessed it), extraordinary circumstances.
The effectiveness of a sacrament does not depend upon the holiness of the minister. This is because the sacraments work in a manner called ex opere operato; that is, "from the work performed." The only limiting factor to the measure of grace Jesus imparts through a sacrament is the disposition of the person receiving the sacrament.