So how does mind over matter relate to spiritual practices? We'll get to that in a bit.
In the practice of Qi-Gong, onlookers look in amazement at the masters of this practice being able to put their bodies through unthinkable acts of pain, without even having bruises or bleeding from it - an act that most people may consider "otherworldly" or "supernatural" - after all, if you just had to have someone hit you full force in the throat with a pole right now as you sit, you will surely die. So, how do they do this? Mind over matter. They describe it as gathering Chi or energy and focusing it at that exact point of impact on their bodies, and "envisioning" (knowing without knowing) that that area has become harder than steel etc - this is usually accompanied by shouts and hitting the area in question. Only highly trained people practice this - and this is understandable, as if you cannot utilize this successfully, death will be the result. The result of this is not just the energy they gather, but them having their brain and thus their own body KNOW that it is invulnerable. Simply imagine the possibilities of what your own body can do! (This does not mean you must try such great feats of will out of the blue - no. Concerning the physical, start small. Lift heavy weights, etc. We will not be held responsible for acts of idiocy!)
Now - the part that you have been waiting for - the spiritual application of mind over matter.
The spiritual application of mind over matter makes use of your own spiritual faculties and of course your will. No need for external forces on this. You can use this for anything whatsoever, and can be included in any paradigm or practice with ease. Say as an example that you have been looking for a new job and have found one that you believe would be perfect, however, you doubt that you will be chosen. The first problem is: doubt. You must remove any form of doubt whatsoever from you, or you will definitely not get anywhere - not even spellwork will assist you due to your doubt blocking progress and movement. You must know without knowing that you will succeed - with no question AT ALL. Next, you must will the result into existence - do not see the process leading to the result, but the result itself. This goes paired with knowing without knowing. See and know yourself as already successful. Then, let it go - this is one of the most difficult things to do, but it is imperative. Not being able to let go, means that you still doubt it, and will thus be unsuccessful. Your will will be hanging in the air instead of being achieved. After all, the success or failure of utilizing mind over matter in any aspect falls solely upon you.
You can apply the above example to any spiritual working. We ourselves utilize mind over matter in all forms of our lives - with great results. So go ahead, take the power into your own hands - what do you have to lose?