The fact that people who want to build muscle ('Bodybuilder') have to train hard - "no pain, no gain" - is very old and incorrect. Nowadays there is scientific proof behind training in general, including the effectiveness of different exercises and how often to train a muscle in order to have the maximum of growth naturally. This lead to a major shift in the fitness/sports world. In the past, many things were told by guys who already did it, which is related to 'bro science'. One example of bro science is the necessity of eating 6-7 meals a day, or your body can only absorb something like 30-50g of protein per meal. If this would be true, the human species would probably be dead already, related to hunting and possibly rare prey.
If you go to the gym without a system in your mind, you will fail yourself sooner or later. For example: In every session, you completely exhaust your muscle (and I'm not talking about cardio). And from workout to workout you may even progress, which means more potential muscle growth. After some time, weeks or months, the progression will stop. You will feel symptoms some of these symptoms:
- being unmotivated
- not mentally fit in terms of concentration
- one or more body parts will start to hurt
- your muscle are always sore and do not regenerate in time
- the quality of your sleep decreases
- the overall performance in the gym stagnates or decreases
- you get sick
Some of these symptoms might be related to each other, but do not necessarily be caused by the same reason. For example, your sleep might be bad if you are personally stressed or the motivation leaks from time to time.
To prevent these things from happening, you should take planned breaks in your training. In these break phases you drop down your training for about half of what you usually do. How long you should do these breaks is depending on you and your training plan, as well as how strong the symptoms are already. For most people, one week may be enough. After that week, you should start some days slowly, for your muscle to adjust. Your body, including passive structures, recovered a bit and you will get stronger than before.
If you don't do these breaks, your body will get them by getting sick or injured.
Your central nervous system
Very important in my opinion is the central nervous system, which is important for motoric and stimuli in general. I experienced the affection of my training on my nervous system, especially when I lift heavy weights. Not only your passive structures (like tendons and ligaments) are under tension. I would describe that experience as 'lack of mental ability/concentration'. Which may lead to injuries, because you are not 100 percent able to do the exercise correctly. If you do these planned breaks, your central nervous system will also 'heal' a bit.