Great question!
A definition is what sets a thing apart from related concepts. You do not need a definition to be able to tell a sandwich apart from a book. You may need one to distinguish a paperback from a folio.
I call myself a mystic, mysticism is a form of spirituality. Spirituality is a form of activity. An activity is a form of agency. Agency is a form of being. Being is a form of existence. I could continue and go down some cool, interesting paths, but this is about my spirituality.
All this meta is important because it is integral to understanding what mysticism is. Mysticism seeks to establish form upon the spiritual world, to distill out the essence of things and apply that essence to seemingly-unrelated things. In so doing I arrive at insights into the core nature of existence.
It isn’t enough for me to know the presence of God. I want to know how that manifests, how it works, where it comes from, what it’s aimed at.
In order to do this I need certain tools. One of those tools is meditation. Meditation alone would not be enough to get me anywhere useful, so the other thing I need is the ability to access the ideas of previous mystics. Mystics I have read in the past in some detail include Osho, George Gurdjieff, Dr. David R. Hawkins. Mystics I have a passing familiarity with include Aleister Crowley, Gautama Buddha. Mystics whose ideas I’m actively exploring include Jesus and Emanuel Swedenborg.
All of these mystics have a different take on the nature of divinity, and different influences. It wasn’t until I had read deeply enough into Hawkins’ work that I could start to effectively do my own mysticism. The ability to do my own mysticism does not make it less worthwhile to keep exploring other mystics.
The forms I discover are of a easily-created-and-torn-down nature. There is a double-sided sword aspect to this. It makes it less easy to publish and publicize my findings. This is why I have not yet written a book, even though I certainly have enough material to fill a few. I just can’t stick to one idea long enough to write a book on it. By the time I can verbalize the form, it wanders off into the sunset to be a character in later stories. I’ve yet to discover the protagonist for my first book.
On the other hand, I would like to enable future seekers to piggyback on my work. I would have never come up with my most recent insight, concerning the twin nature of spiritual growth, articulated here, without the previous work I’ve done to understand Hawkins. If I never capture my findings, then I won’t be paying it forward to future generations. So I need to find a way to do that.