If you really want to become a horizontologist, you also will want to become a body builder. This does not mean going for the typical Mr. Universe physique but rather keeping the body strong and limber especially the lower back and abdomen.
Proper sitting as in aguira style or seiza style tones your lower back and abdomen as these muscle groups work together to stabilize your seated posture. Try getting an opposing muscle group exercise that is constant and effortless while sitting in a chair!
The horizontologist rises with the sun but does not rise until the eyes are open, the body is prone, the hip joints are stretched and rotated, the knees are bent to the chest, the shoulders are rotated, the arms reach.
Concentrate on good posture when walking. Walk like a king or a queen (a good one). Seek out plenty of fresh air and sunshine. Breathe in deeply and turn your face to the sun. Eat small meals throughout the day. Do some hard work. Do some lying down.
Can you lie down flat on the sand? Or flat in the grass? On the sidewalk? Many people cannot lie flat after years of verticality. Did you build your body today or did you dismantle it?