Do you sit with your back straight all the time? I won't find many people that say they do. Most people don't think about their posture in everyday life, there's just too much other stuff going on, but little do people know it is very important to prevent injuries and even improves mental strength.
Physically, if you were to improve your posture you may also be enhancing the biomechanics of your body. In simple terms, having poor posture in your upper back may lead to muscular problems in your lower back as a result of taking the additional stress of supporting your shoulders. As a consequence, the upper back will weaken due to not engaging properly.
Another example of this problem is when we sit. Our bodies were not designed for prolonged periods of sitting. When we sit for a long time people may complain about tight hamstrings or pain in the legs. You're probably wondering why this is! It is due to the tightening of the piriformis and gluteal muscles (bum), affecting the biomechanics of the whole leg and causing the hamstring to work harder, hence the tightness.
To combat this you should get up from your desk/sofa/bean bag and walk for a few minutes periodically and concentrate on walking with your shoulders, back and head up right. Not only will this help with your biomechanics but also help your mental strength, feeling more confident and ready to take on any task.
If you feel you have biomechanic issues (most of us have) don't hesitate to contact me and I will screen your body and assess what corrective exercises I can implement to help you live a more comfortable, healthy life.