Everyone should take this moment to consider correct posture.
One of the best pieces of advice I ever received was to change the angle of my rear-view mirror to remind myself to sit straight.
In essence, try to force the lowest part of your neck to touch the heighest point on the headrest.
Then notice how you cannot see out of your rear view mirror. Adjust it from this position, and get used to it.
It's gonna be weird for a while, but I assure you, this is what is best for your spine. I'll take your gratitude in advance, for when you're 80 and not folded over.