"healthy existence" = healthy living or healthy lifestyle.
...as in eating healthy food and staying fit.
"human existence" = human life
"health care" as in you have a good doctor, a hospital near by in case of an emergency, good medicine. If you are sick will you be cared for.
Example, when you cut your finger, you wash the cut, disinfect, bandage the finger. This would be a single example of a sound health practice.
"sound" as in solid or proven.
"healthy" as in good for you.
"practice" as in method or actions taken.