The root of the word "Mystic" itself is connected to the word "secret," which seems fitting: most of us probably associate "Mysticism" and "Mystics" with something like secret mountaintop communities, where hermits gaze into crystal balls and commit their lives to secret techniques for transcending the physical world. But in truth, few Mystics would be able to relate to such an inaccessible way of life. The reality is that the Mystic path is accessible to everyone – adjacent to the life you're already living – and is only "secret" in that it's historically been overshadowed by mainstream, institutionalized religion. But now, as more people are seeking hope in the face of disillusionment with religion and despair about Earth's future, the Mystic way is growing in prominence. So what does it mean to be a "Mystic?"
First, I should note that many mystics would prefer to leave the word “Mystic” un-capitalized, to reinforce its distinction as a (possibly the) spiritual tradition accessible to all people. Personally I prefer to capitalize it for the time being, to reinforce its distinctiveness as an ancient and still-vital spiritual path, to help lend the term more visibility and credence in our modern consciousness. Beyond this, a good place to start is addressing stereotypes. In The Big Book of Christian Mysticism, author Carl McColman debunks some common misrepresentative stereotypes:
Mystics are not confined to cloistered or hermit life
Mystics are not obsessed with obtaining ecstatic experiences, consciousness, or abilities
Mystics are not obsessed with obtaining arcane knowledge and rituals
Mystics are not confined to rootedness only in Eastern spiritual traditions
McColman goes on to set the record straight. In the historical Mystic tradition (and in my own words):
though contemplation is essential to spiritual depth, “getting your hands dirty” in the practical world of community, service, and justice are even more central; so we (1) seek both solitude and solidarity
“peak” experiences are ultimately no more than “peek” experiences – almost all spiritual richness is found in life’s mundanity; so we (2) seek both the wondrous and the workaday
though institutions can help organize the spiritual life, all you need to know and do to be a Mystic is relate to life spiritually; so we (3) seek both structure and spontaneity
all spiritual traditions have Mystic heritage, and thus the ability to embrace all other spiritualities; so we (4) seek both rootedness and relationality 
Looking at these four principles, we might now say, “Isn’t this refreshing? Any of us could be a Mystic – Buddhist, Christian, Hindu, Jew, Muslim, Neo-Pagan, Secular Agnostic, Taoist, and Yoruba alike!” This is true! If we paint a picture of the Mystic life, it probably sounds like your own!
Then we might also say, “Maybe that even means all of us are part of a universal, all-encompassing Mystic tradition, even if we don’t know it!” Maybe. However this leads us to an important debate. Some skeptics claim that while there may be “Mystic traditions,” there is no universal “Mystic Tradition” – such a notion is merely a New Age contrivance that homogenizes the actual traditions it claims to unite, and thus dishonors them. Which side of this debate is correct?
As a Mystic of any tradition would say, the evidence shows the full truth is more complex than anyone can claim to know. The best we can do is hold all the conflicting truths together and embrace the messiness of reality, acting only with intention and care. So the skeptics are right: there has never been one world religion, and it’s wise to be dubious of attempts to claim something like one. The past shows such attempts have often harmed people and ancestral lifeways.
Yet, even while our sanitized history obscures these horrors, we also underestimate just how similar humans and our experiences are biologically and psychologically, as well as how interconnected the world of the ancient Mystics was by technology, trade, travel, and ideas. Moreover, the more we examine seemingly disparate spiritual teachings, the harder it is to ignore a sense of uncanny convergence. It’s this convergence that entices the singular – tradition. So what do Mystics converge on, other than the four debunkings above?
In the meantime, I offer you some reflection questions:
How have you been cultivating the four principles above in your life?
To learn more
 Carl McColman, The Big Book of Christian Mysticism (Hampton Roads Publishing: 2010)
 Richard Rohr, The Naked Now: Learning to See as the Mystics See (Crossroad: 2009)
 Karen Armstrong, The Case for God (Knopf: 2009, 2001)
Mirabai Starr, Wild Mercy: Living the Fierce and Tender Wisdom of the Women Mystics (Sounds True: 2019)