6) You’re not addressing your weaknesses or injuries.
Muscle imbalances (strength or length) and pre-existing injuries can affect each rep. Glute and lower trap inhibition and dominant hamstrings and upper traps can all affect how the muscles surrounding the joint function. They can also result in postural issues and joint dysfunction. Bum knees and shoulders can continue to deteriorate if you do not change your exercise selection and address your limitations. Choose your exercises wisely to add strength and function to your body.
Regular massage treatments or self-myofascial release can address soft tissue issues. A proper warm-up consisting of light aerobic exercise and appropriate mobility drills can not only prepare you for the workout ahead, but can also address range of motion issues.