A poor posture is bad for your health in the long term. Whether you work on the computer all day, sit in a chair all day at work or at school, chances are you are slouching and don't even realize it.
It doesn't look nor feel good. Over time, you will find out why ignoring it was such a bad idea.
You can wear it invisibly under your clothes and let your body get used to the correct posture at an easy going pace. Wear it as often as you like, and after time you won't need it to keep a good posture. Your muscles will have adjusted to your new improved position.
Lower back pain, spine deformation, nerve compression resulting in pain shooting down your arms or legs, headaches, and much more. Once you have these problems, it may be too late.