Learn to sleep so you head and neck stay straight throughout the night. I learned to sleep on my back with my head only supported on the sides so it does not roll to the side. Sleeping with the head elevated is a learned behavior. It can be unlearned. I learned that the head tilted forward was the worst position for me.

If your neck gets stiff, there is a reason. Find the reason, correct it and be disciplined so you do not undo the correction made.

I've used chiropractors and a highly skilled Physical Therapist and over an extended period of time, my neck became stabilized and my stiffness and other problems subsided.