Tip of the Day: Ways for Better Posture
Don’t worry about putting your shoulders back. They’re probably rounding forward because your neck is poking forward and your ribcage is collapsed.
Take 5 or 10 minutes out of your day to lie on the floor on your back with your head resting on a few inches of paperback books. Have one or both feet on the floor, knees bent. Let yourself breathe slowly and fully.
If you have to slump, slump. Then slowly get out of the slump by letting your head lead your torso into length while your sit bones release down into the chair.