What should I do on a daily basis to prevent my face from sagging?

I'm worried because my facial elasticity isn't what it used to be, and I feel like it's sagging little by little. Seeing how the corners of my mouth and jawline are becoming subtly blurry, it suddenly struck me that I need to take better care of my skin before it's too late.

While dermatological procedures are great, the cost is quite steep, so I am first looking for preventive measures I can practice in my daily life. I plan to get the procedure done after that. Some people have advised me to get into the habit of sleeping on my back, saying that sleeping on my side causes the face to tilt to one side and worsens sagging. They also mentioned that resting my chin on my hand or constantly bowing my head while looking at a smartphone ruins my facial contours. So lately, I have been consciously trying to maintain good posture.