Mysticism is a level of Catholic spirituality not easily achieved. Traditionally, in the spiritual life, one begins with the purgative, fighting one’s bad habits and temptations and avoiding sin. Mortification and penance are encouraged at this basic level. Next is the illuminative level, seeing the light of truth by cultivating the moral virtues and seeking to do good rather than simply avoiding sin. The third level is the unitive, in which one has an intimate communion with God. Here is where mysticism takes place.
Meditation is practiced in the second level of the illuminative, but it is contemplation where the mystic finds a home. Meditation is the intentional concentration of the mind (intellect) on the mysteries of faith in the Christian religion, for example, the Incarnation, the Trinity, and the Real Presence. It can use the senses, imagination, memory, and emotions.
Contemplation, on the other hand, is not conjured up by the person, but is a gift from God where He communicates cor ad cor loquitur (heart speaks to heart) in the quiet recesses of the human soul. Only intimate union with God can allow for true contemplation. Those who achieve it are considered mystics or contemplatives. Saint John of the Cross, Saint Teresa of Avila, and Saint Ignatius of Loyola are famous Catholic mystics.
The object in contemplation is not contemplation itself, as is the case in pagan and non-Christian mysticism. The goal of contemplation is holiness, to seek sanctity by getting closer to and getting to know better the source of holiness, the Holy of Holies, God Himself.
When attachments to this world, to things (possessions, money, power, pleasure) are abandoned, then attachment to other things needs to take place (recognition, thanks, affirmation, consolation, appreciation). Finally, the self (ego) must be destroyed, in what the mystics call “dying to self.” One’s will must be sacrificed so that it can be replaced by God’s will.
Saint Catherine of Siena experienced mystical ecstasy where she levitated from the floor and would simultaneously feel pain and joy in her body and soul. Saint Francis of Assisi and Saint Padre Pio of Pietrelcina were mystics who were also blessed with the Stigmata (having the five wounds of Christ on their own bodies).