Manifestation, Mind-over-Matter, the Power of Positive Thinking... these are all powerful tools, when properly employed and well-understood. In less ideal circumstances, much confusion, frustration and disappointment may result instead.
Mysticism does not force. Positive thinking, manifestation, mind-over-matter are naturally achieved when conditions are perfected (or merely improved). This natural development requires quite different means than the forceful approach, and is driven by a unique underlying philosophy of Life. The mystic honestly believes (or endeavors to believe, through experimental trial & error practices) that Life, the Universe, the Divine, is a genuinely benevolent Force, ever working towards our betterment, and is constantly attempting to bring us abundance, grace & contentment. The mystic becomes wholeheartedly convinced that he/she him/herself represents the greatest & primary obstacle to this perfect Life constantly, presently & currently being gifted from the Divine.
This is not entirely at odds with the power of positive thinking, mind-over-matter, etc. However, an important feature of divergence to note is that Mind is only one factor, Emotions, likewise are only one factor, and while uniting the Mental, Emotional & Physical bodies is the key, we often overlook the power, influence and reach of the subconscious & unconscious elements at play within each of these bodies. Working with our Spiritual (Divine) force is the only way to rectify this situation successfully. Forcing positive thoughts, emotions, actions, etc, while there are deeper, internal feelings to the contrary is not only ineffective, but also greatly counterproductive.
We tend to fear (consider the implications of this statement for a moment) that if we do not 'get rid' of our unpleasant emotions, self-sandbagging thoughts and/or destructive behaviors, that we will end up in dire straits. There's Truth to this, make no mistake. However, the procedure selected to solve this makes the difference between success and 'failure' (failure always being a temporary [aka temporal] condition with respect to eternity).
In modern societies, we are so accustomed to force as a way of life, that we now have little to no faith in the beneficence of Natural processes. We trust Nature just exactly as much as we ourselves are trustworthy. This is, of course, as case of what psychology would likely term 'projection'. Thankfully, Nature is not as fickle as we, but is in reality completely reliable.
Our problems with Nature, as with all our other problems, stem from our own discordant inner 'harmonies' or 'advances'. We see this clearly in the history of technology, as we endlessly progress by finding solutions to technologically created disasters and/or inconveniences. We need not become Luddites, but perhaps more time & energy spent on considering effects before financial profit would be generally advisable. The commercialization & monetization (termed 'rape' by the more emotionally charged amongst us) of Nature has directly led to our lack of trust in Her. Nature tends to push back when we try to steal Her lunch money, Heaven forbid! Like it or not, this is an unavoidable Truth, despite our best efforts & crack minds ever on the case.
From the world stage, we now shift to the level of our personal lives, where we must likewise learn to trust Nature again, rather than panicking into a flurry of activity & efforts, 'doing our best' to prevent the growth that Nature has presented us with. This very often worsens our problems, and in extreme cases, can make them entirely unsolvable within the span of our personal life. As Soul Beings, we cannot be eternally harmed, this is true, but we can create such a mess of our bodily situation that we may not be able to reverse the damage, absent a miraculous (Divine) intervention.
This being the common plight, the mystic focuses little on technological (human/mortal/earthly/etc) science, and primarily on the 'science of miracles', which, contrary to popular opinion, is in fact a repeatable & scientific approach. The mystic, rather than trying to create miracles, believing that miracles are actually the natural state of the Universe, asks the question, "What exactly is currently preventing this natural, miraculous state from manifesting?" The mystic begins to 'look' for that which he/she believes to be there, recognizing that the deficiency is either within his/her (inner) sensing functions, or more likely, no detriment of function, but simply a lack of conscious focus on them.
As a consequence of our search, we will encounter endless subjects of gratitude arising, naturally generating feelings of positivity, and we do not feel quite so critical as before. We begin to see that negativity & criticism are not native to us, but rather we have carefully cultivated & fed them, requiring great amounts of energy, focus & time to sustain, create and generate. We feel less like asking "Why me?!" In an accusative tone, and instead feel compelled to exclaim, "Why indeed am I so blessed?!" The answer being that it is the nature of the Divine to unceasingly outpour Its Love, intrinsically.
To aid our practice, we continually ask for Wisdom to understand and accept those circumstances that we do not yet appreciate, and for the Grace to prevent our doubts & fears from causing us to take actions that will just mire us deeper in even more difficult conditions. We can relax into stress, sorrow, pain, not in a wallowing fashion, just not struggling with a need to change them. When we wait upon the Divine (and this is where Mind over Emotions & Matter is useful), the Divine arrives, at the Perfect time, with the Perfect solution, sharing Perfect Comfort & Love. We simply admit and accept that we need the Divine Presence, and will not attempt to fix or improve things ourselves from a place that we know we cannot (the egoic / persona level).
The Divine makes all things new. Let us ever learn to wait and place our full Faith Therein.