When trying to fix posture is it important to sleep on your back and sit up straight

[davidgandyfanboy]

This might sound dumb but I've never seen anyone promote these things for posture training, only posture exercises

 

[chudinarug]

This might sound dumb but I've never seen anyone promote these things for posture training, only posture exercises

sit up straight yes to an extent
sleeping on ur back no, will likely cause mouth breathing