The difference between religion and spirituality
Religion, at best, leads to spiritual mysticism.
Religious institutions resemble educational institutions in that the latter provide structured indoctrination, behavioral training, socialization, and conformity under the direction of authority figures who espouse dogma. The dogma often originates from the teachings and examples of certain revered historical figures but is interpreted and organized by scholars and administrators. Various rituals are employed. Motivation is provided by a reward/punishment system.
The success of schooling depends on the quality and aim of a given school's administration and faculty, and the ability of a given student to benefit from the positive influences of the school while resisting the negative influences. Some graduates achieve full self-hood and become independent, self-motivated and self-directing, creative and original, rational and intuitive, and capable of critical thinking. Many, however, fail to achieve their full potential and remain imitators and conformists.
Great intellects, or geniuses, must first learn conventional wisdom and then transcend it by questioning accepted orthodoxy in the pursuit of truth, even at the cost of peer esteem and professional status. Likewise, great spiritual seekers, or saints, are those who have transcended officially approved belief systems, even at the expense of a secure place in their congregations, and have experienced an awakening in consciousness: a direct experience of truth. The awaking may or may not have been facilitated by religion, and the awoken may or may not continue involvement with religion.
Spiritual seekers seek the spirit or intangible essence of self that lies beyond worldly perception and beyond doctrines and dogmas. A monk-like introspective phase inevitably occurs, often in solitude, in which depths of being are gradually revealed as the superficial, conditioned, socialized persona peels away through meditation and prayer. As the monk uncovers previously hidden or dormant dimensions of being, mystical experiences become the norm and a transition is made from monk to mystic. The mystic may then return from solitude to enlighten those still mired in ignorance.
We might describe as mystics those who seek to know what is hidden, who penetrate the "myst" or fog of conventional perceptions and beliefs, whether they are of the intellectual or spiritual variety. And since truth of any variety is truth, the distinction matters little.