I have grown convinced that 90% of physical fitness results from eating healthy while refraining from eating tempting foods that taste great, but actually destroy the body (immediately or over the long haul).
I've also found the same is true about the spirit. God created us to live in obedience to His Word while refraining from tempting decisions that taste great for a short season, but destroy the spirit as well as our potential.
At the end of the day, we are what we eat. We become what we devour - physically & spiritually.
"Man shall not live on bread alone, but on every word that comes from the mouth of God" - Jesus (Matt 4:4)