When sitting, you can sit on your  Coccyx, or your Ischial Tuberosities. After all, it’s your ass!

BUT…..sitting on your coccyx  ( right picture above: Boo. Bad) is the same as bending over badly and slumping (bad): the abdomen protrudes (bad) , the chest sinks ( bad), and breathing is inhibited. (cannot be good) It also indicates  fatigue (yawn) , and lack of support (Boo). In this position you can  try and make the client  (or yourself) sit up, but it will only last a short time before slumping back (sob) into your Backaholic patterns
Sitting on your Ischial Tuberosities ( a good place to sit, on the left above) , causes a more upright position (good), which elongates the spine (good)  and reduces excessive curvature (good; high five) .  Maintaining  this natural spine is easier as it is seen as a natural position (good. Fist bump). Each minute of wrong sitting can be compared to doing  the wrong exercise. if you sit poorly for 8 hours a day, thats a lot of bad exercise.  you are not a runner or a body builder or a crossfitter, you are a “bad back maker”
Of course, you should never sit  for that long, but if you must sit, sit on your Ischial Tuberosities!!
To get into correct “sit”, once you have sat down, lean to one side (imagine you are  trying to break wind!)  and gently lift your “lifted” buttock up with your hand,  scoop it back then sit down, then do the other side.
This said, you still  have  to fight your slumping habit. You must learn to sit tall and relaxed, but with an appropriate amount of abdominal tone. Say No to being a Backaholic!!