On the contrary; for anything even approaching the best possible results from training, it is absolutely essential to work in direct opposition to your instincts. If you followed your instincts, you would do quite a number of things -- eat as much as possible, sleep whenever possible, defecate, fornicate, lie, brag, steal, run away from danger or fight if simply forced to or if faced with an obviously inferior foe in possession of something that you desired, and avoid any form of physical labor -- but you wouldn’t lift weights.
The process of education is nothing more or less than an attempt to overcome the instincts -- and it is seldom if ever totally successful; while heavy physical training may -- and frequently will -- result in a feeling of great personal satisfaction, such a feeling is entirely due to conditioned reflexes, not to instinct.
During the actual performance of any form of exercise -- with the possible exceptions of fighting or running away from danger -- the instincts are almost literally screaming at you to stop; and if you follow those instinctive urges, then exercise will always be terminated far short of the point that would have produced any worthwhile results.
The body will do almost anything in a effort to maintain the status quo -- and it is fully capable of anticipating needs with a great degree of accuracy; instinctive hunger pangs proceed the actual need for additional food by as much as several hours -- and when any form of exercise is undertaken, the body quickly recognizes the trend and attempts to stop the exercise long before a point of exhaustion is reached.
A very commonly observed symptom following the large scale loss of blood is a total aversion to any activity that might possibly result in additional blood loss; the body cannot then stand much more blood loss, and does everything possible to prevent it. And it is not necessary for a blood loss to be on an actually dangerous scale for this symptom to manifest itself; the body attempts to maintain a definite, but unknown percentile of reserve -- and when this reserve is threatened, the system will try to prevent additional utilization or loss.
An exactly similar situation exists in regard to reserves of strength; when a particular workload closely approaches these reserves, the system will rebel against the imposition of any additional workload. But unless a workload does fall well inside the momentarily existing levels of reserve strength, then no demand for additional muscular growth or strength increases is imposed upon the system.
So attempting to follow your instincts will get you literally nowhere in physical training. Obviously there is a limit beyond which you should not go, but this limitation applies only to the actual "amount" of exercise -- not the intensity of effort; maximum intensity of effort is an absolute requirement for the greatest possible degree of growth stimulation -- but it must be achieved without totally exhausting the body’s recovery ability.