The SBS/SAS and Navy SEAL Special Forces Training courses are designed to physically and mentally test the Trainee and how he thinks to the absolute limit.
So much so, that your initial reasons for wanting to become an SBS Combat Swimmer/Frogman, Navy SEAL or SAS operator all but would have dissipated like snow in the sun if it was not for your ability to access the power of the mind.
Once that subtle barrier to the mind has been passed, the Trainees are able to take control of their thoughts. Feelings of fear, anxiety, stress, exhaustion or any other aspect that would hold them back are now being controlled by the power of their sub-conscious mind. They are able to will their bodies to continue indefinitely under any circumstances, while undergoing physical conditions and mental demands that would otherwise be humanly impossible to achieve. This is also known as the power of the sub-conscious mind over the conscious mind or Will-power.
Once a Trainee reaches this Phase in the training, usually nothing will stop him, and he would be able to continue under these circumstances almost indefinitely unless he becomes injured, which sadly does happen from time to time. This Phase in the training sets the stage for a total identity change and a tremendous boost in self confidence. The concept of something being impossible is broken forever. This is why the SBS/SAS and Navy SEAL Special Forces are able to undertake operations and endure physical and mental conditions that for others are all but impossible.
The trainees have reached the stage in their mind that turns all negativity into positive objectivity with the trained, inbuilt desire to always find a solution that will turn any negative experience or set back into an immediate or long term possible, positive outcome.
Leave the thinking to the horses; they have much bigger heads than you. That was the reply from one of the SBS instructors in response to a trainee