You should always have a routine that is going to exercise all of the muscle groups. For example, males tend to do a lot of chest and arms, but neglect their back, shoulders, core muscles and their legs. If you do not have strong legs, then your foundation is weak. If you do not have balance between your chest and back muscles, then your shoulders will start to round forward creating unnecessary tension. Practice working all of the major muscles including the opposing muscles.
Oregon Personal Trainer