I am catching up with posting online my articles.
Thus during hard training the body is using its own resources which cannot be replenished and this is the reason why many people get actually burned out. And you may motivate yourself to train hard for some time ( e.g. 3 months ) and push your body through the pain and you may get the results ( gain with the pain ) but if you reach the phase of the burn out or if you get sick then you are not going to be the model for the magazine cover. Have a look at the top athletes and sportsmen after they finish carrier. Many of them get fat, out of shape and sick. And this is the result and consequence of pushing the body through the pain with the desire to gain.
Thus the gain is only temporary and sooner or later you will lose and thus our famous statement loses its validity again.
Here is another point...
Hard training with pushing the body through the pain usually causes accelerated wear and tear of the joints, tendons and bones which consist of tissues which repair themselves at relatively very slow pace and thus here comes the element of pains and injuries which in many instances are irreversible. Obviously this type of problems is not visible immediately but in the end it is the consequence of pushing the body over the limits ( the pain ). And so the gain is only temporary.
Thus as you may see the statement "no pain no gain" is valid but only as long as you look at it in a limited and ignorant way because you do not take into consideration all aspects, elements and dimensions and simply speaking you do not look at the big picture.
Here is the last question...
Have you ever considered the concept of gaining and succeeding in an easy way and with joy, which would be the opposite to the "no pain no gain" ?
Try to investigate and find the answer for yourself...