PRINCIPLES OF EXERCISE:
There is no good or bad exercise. Rather, it is the correct exercise for the person, at the correct time and performed correctly.
Exercise is a stress and every session has a cost. Balance your training with the proper amount and quality of recovery to ensure the effects are positive.
Fitness is made up of many factors. The fitness to run a marathon is very different from that required to sprint 100m, throw a discus compete as a bodybuilder. The type of training you perform should be specific to your goals.
Like the saying goes, if you fail to plan you are planning to fail. Get clear about your goals and set objectives for your training.