IT is a way to look at things. But, In the modern US military Special Forces soldiers use a combination of training, conditioning, and mental fortitude to push the envelope of physical tolerance. There is no religion, philosophy, or mystical energy in these teachings.
Snipers can lower their heart rate, metabolism, and pain tolerances through intense concentration and breathing training. It enables them to do things like stay absolutely still for upwards of 10 hours at a time, watch a particular target area with keen alertness for hours on end, and still maintain instantaneous fine motor control for quick and precise target adjustments.
Navy SEALS can control their core temperature by manipulating their bodies metabolism to produce more heat even while not exerting muscular force. Simply by repetitious training and conditioning. During BUDS training (which lasts 7-9 days) they will get on average of 15 minutes of sleep every 8 hours and will go no more than 25 minutes continuos sleep in that period. Yet they have to maintain the mental alertness essential for handling explosives, dive mechanics, weapons management, safety procedures and much more.
Greene Berets (specifically ODA's) use the same skill sets from all of the above and, as their primary role is a force multiplier, must be able to adapt themselves to regional customs, languages, foods, and more in order to gain trusts and train and command indigenous forces.
Delta Force (SFOD-D) operators are deployed operationally all over the world in any situation imaginable. They are trained in SCUBA, Explosives, Sky Diving, weapons, hand to hand, languages, communications, covert cover and spy like tradecraft, covert surveillance, urban assault, burglary, and about a ten thousand other aspects or disciplines. Not to mention that every one of them is a trained sniper. They can enter a room and engage up to 5 targets (while accurately assessing threat priorities) placing a round from a handgun within 5 millimeters precision over a 30 foot span of room filled with absolute chaos in under 10 seconds.
Bruce Lee was an exceptional human who pushed his personal physiology beyond the breaking point to many times. The human body and mind, when properly motivated, are capable of tremendous feats. I have been a martial artist for 15 years. I have heard every kind of physically mystical attribution imaginable in that time. Though I have never seen anything that can not be achieved similarly by either repetitious training and conditioning or by managing you adrenaline levels(again through the benefit of training and repetition). No mystical forces or complicated rituals are needed.
In fact, Bruce Lee invented Jeet Kune Do with the express intent to remove the unnecessary bits from the the martial arts in order to achieve the fastest and most direct path to victory.
I was indeed talking about Hell Week.