Mysticism tries to bring oneself to a union and awareness of and with God. It teaches you to believe (or understand) that you and God are one, that God is in you and you in Him, and to realize (or be aware of, is the better term) the presence of Him is in and of everything in the universe. Your consciousness (or spirit, soul) comes from the Life Force that is God, (but don't think of God as just a "Life Force", that's not Him at all, you watch too many movies) which means that makes everything living, a part of Him. Everything in the Material world and Spiritual world is of God. Mysticism also teaches that God did make man in the image and likeness of Himself. Meaning, He has the same human characteristics as we do, but infinitely more so. He has love, compassion, warmth, humor, irony- things you'd only think you'd see in a human being. But that is what makes humans so special, because we are literally the image of God. He is the Original Soul, The Being that always Was, always Is, and always Will be. Just like the souls you and I have. He laughs and makes jokes, He can feel, He thinks, He's infinitely creative, everything humans can do He can do infinitely greater. Don't think of Him as separate or different from you, He is exactly like you, only Perfect in Goodness (His Will Is only Good). This is why He so loves us and always has compassion for us.
Mysticism only tries to help you realize this concept that people have forgotten. Its the basis for life. Its in Scripture. It does state we are the Image of The Living God, we do have the same qualities as Him, He does infinitely love us, and we are a part of Him. It states that He is everywhere, in everything and of everything. It states that He is The Alpha and The Omega, The Beginning and The End, The First and The Last. He knows what we do, what we see, what we think, what we hear, what we take to heart, what we ignore in our hearts. Nothing is hidden from God.
The definition of Mysticism is really misunderstood. Yes, you probably shouldn't go so far into it if you don't want to, because you don't know what you might get into. But I'm telling you the parts and concepts of it that aren't bad, and are encouraged in the Bible. If you'd like, you can meditate, whether silently outdoors, or indoors while reading the Word. Meditation on the Word is appropriate, and is what you do every time you read the Word. You read it, understand it, take it in, and maybe believe in it. Meditation outdoors just brings you back to reality that you live in this huge vast never ending universe. You smell the fresh air, the birds chirping, the bees buzzing (unless it's winter), the feel of grass (or if you live in the desert, dirt), the beautiful sky (whether its blue or gray, God made it beautiful) the wind blowing in your ears and on your face. This is all meditation is, and it brings such a peace to you that you won't imagine. It silences all your thoughts, and brings you to reality that all is well, and you are alive, and there's a God who loves you and will never ever stop. It shows you what truly matters in life.
So, that's all mysticism is. Just trying to have you know God more. At least, that's my take on it.
Edit: I encourage reading the book, "Proof Of Heaven", by Eben Alexander. It's a #1 New York Times Best Seller and definitely worth the read. You might learn things that you've never understood before about the spirit, the spirit world, the physical world, and even the brain (how it doesn't produce consciousness, unlike opposite theories of other scientists). God Bless!