First of all, it may be that your training frequency and density are too high, so that your muscles don't have enough time to rest. You try to take a day off after training, that is, four days a week, and rest and recover after training every day. This is also a common problem for beginners.

The second possible reason, the good feeling in fitness is the so-called "pumping feeling", which refers to a muscle congestion phenomenon caused by the increase of body temperature and the acceleration of blood circulation under a certain intensity of training. Accompanied by this phenomenon, you will feel physically and mentally energetic, and your training state will be good. If you haven't felt this "pumping feeling" for a long time, there are many reasons, perhaps you haven't had a good rest, your sports skills are wrong, and so on. But usually the most important factor is that your attention is not enough, and your psychology is boring and monotonous for training, which can also be said to be a lack of passion.

The third reason may also be that your daily nutrition can't keep up. Every time after a large amount of training, it will bring you different degrees of muscle fiber tear. At this time, it is very important to supplement protein and carbohydrates, which can promote the recovery of your muscle fiber tissue and physical strength. If your nutrition is not proportional to your training intensity, the muscle tissue damaged last time has not recovered, and the energy (ATP, glycogen, etc. The energy stored in your muscles has not recovered. If you do this kind of training again, your muscles will certainly be depressed.

The last possible reason is that your training movements or skills are wrong. For example, if your posture is wrong, it will lead to changes in your stressed parts, and the actual effect of the parts you originally planned to practice is poor, which may also lead to your "feeling".