The internet is saturated with advice around maintaining good posture (guilty!), but it's not as if you'll be dragged off to "bad posture" prison so what's the big deal? Your muscles start to tighten up, weaken or become inhibited to establish your new "norm", but these norms aren't ideal for everyday living. You're not just going through your day sitting and standing every moment of your day. You also carry things in awkward ways, bend over to pick something up, skip, jump, work out and move in all sorts of ways. "Poor posture" wears down your body so that when you do these things, especially if you're working out in the gym, you're more likely to pull, tweak and injure something.
So, not paying attention to your posture just hurts, in more ways than one. Check the video at the link below to learn more about how our spine is supposed to be aligned, what to do to work on your posture and finally understand why we keep writing about good posture.
The benefits of good posture [TED-Ed]