The flesh leans on its own power and its own wisdom.
It is the performance of man to feel good about himself in order to get the approval of man. It is also competitive and causes you to be striving in self power to be someone, to build a name for yourself and to have fame.
This puts your whole being in stress mode, but your nervous system will surely suffer, contracting disease.
This is of course contrary to the way of the Spirit, where we lean on His wisdom and understanding.
“Trust in the Lord with all your heart and lean not unto your own understanding. In all your ways acknowledge Him and He shall direct your path.” Prov. 3:4-5
It is so easy when you are led by the Spirit, not fulfilling the lust of the flesh. Life becomes a song, without striving and stress. - simply flowing in the power of the Spirit.
Your body is energized by the Spirit with His resurrection power and you can enjoy your life fully without worry, stress and fear. Divine health is your portion and God is glorified!