Imagine someone lifting you up by your hair, toward the ceiling.
Don’t work so hard at perfect posture that you get fatigued. Try lifting your breastbone up by just 1 inch. That’s easy to maintain.
Be sure that your knees are about 1 inch lower than your hips.
Walking, and especially sitting, with your wallet in your back pocket causes pelvis and spine misalignment. It’s a significant cause of low back pain and even limping! Thin it out and keep it in the front pocket. Definitely don’t sit on it!
If you need a little support while you’re practicing neutral spine, try a towel. Fold it in half/quarter and roll it up as shown. Place it in the small of your back, in your lumbar curve. This will help you maintain neutral!