You've determined that the aches, pains and tension you feel may have something to do with your 'poor posture', or with 'stress'.
But what is 'poor posture', really? How did you get there, what do you do about it and why is it so hard to maintain better posture?
First, let's define 'posture'.
More than how you sit or stand or move, it's your relationship with whatever you are interacting with, or trying to accomplish (within the constant downward pull of gravity). Your posture can be healthy or unhealthy, based on your alignment and appropriate positioning of all your parts.
Another word for posture: 'habit'. You can have healthy habits or unhealthy habits. But either way, habits are formed and reinforced around what you do the most, usually without a real awareness of what's happening until stuff hurts. We are shaped by our habits, and they become our posture.
Another word for stress: 'workload'. It is what it is. But how well you bear up under it depends greatly on your posture.
We tend to have a simplistic approach to dealing with posture, habits and stress. If we're slouching, the logical assumption is to sit or stand up straighter. If sitting too much is the issue, then, well, we should stand more, or exercise more. If we're in pain, we seek relief in the form of bodywork, stretching, PT, medications or surgery. If something is 'causing' us stress, then doing away with the stressor and replacing it with ease is what we long for.
But these approaches tend to overlook how the body actually works, and what it really needs. Healthy posture, like any other healthy relationship, requires a more holistic approach - beyond band-aids, adaptations, and superficial reactionary measures.
It requires going a bit deeper, paying attention to how your use your body all the time, bringing it back into alignment, and consciously forming healthier habits.
So, how do we do that?