I don't know.
A lot of people argue we can be spiritual while we're doing physical stuff, but I'm thinking the truth is somewhat further down the road. I'm just not sure where.
The Lord is very clear, and His disciples after Him. "The kingdom is not meat and drink; but righteousness, peace, and joy in the Holy Spirit." Physical stuff is not the material of the kingdom.
I'm currently experiencing a thyroid deficiency. I function normally until I suddenly hit an energy limit, after which I barely function at all. From that moment until I recover, hours or days later, I judge every person harshly, make mountains of molehills, and find joy in nothing. There's nothing grossly wrong with me, just a tiny hormone imbalance, but my contribution to the goodness of the kingdom plummets. Every relationship in my life is tested, and I'm helpless to contribute positively. It's all I can do not to undo the good I built when all was normal.
My standing before God doesn't change one whit, and I turn to Him in those times, not away. This is not a faith issue. My spirit may even be mysteriously strengthened in some way in the midst of this trial, but I'm confusing and hurting people I love. His grace is sufficient for me, and for those whom I love and hurt, but this little thyroid imbalance reverberates painfully through my little corner of His kingdom.
Eating well, sleeping well, and exercising wisely, the things that keep me within my thyroid's limits, become spiritual disciplines. Should I spend fifteen extra minutes preparing wise food or praying? It's a toss up. The contrast is clearer if I throw in a third option, like watching the latest tennis match. A trashy meal or a skipped prayer won't crush my thyroid, but a missed TV show might actually help it by making time for me to eat, sleep, or exercise. Doing right things might make a positive difference for someone tomorrow.
If physical things become spiritual in times of duress, are they not always spiritual? I think they are. More and more, I believe Jesus was looking forward to the day He would get to cook fish for His friends, the day He'd really need a long drink of water, the day He'd fall happily into bed and enjoy His fill of much-needed sleep. I believe Jesus desired to put on flesh even before His death became part of the mission. Jesus must want to relate to us physically, because He was certainly under no obligation to create such a physical world. Jesus must love this world and His people as the sweaty, real, amazing things He created us to be.
Since I'm still an old 'Damentalist (I take the "fun" out of "fundamentalism") I'll share with you a scripture that persuades me.
Mat 25:34-36The King relishes shared, physical acts. The kingdom may not be meat and drink, but it is awarded to those who share their meat and drink.
Then shall the King say unto them on his right hand, Come, ye blessed of my Father, inherit the kingdom prepared for you from the foundation of the world: For I was an hungred, and ye gave me meat: I was thirsty, and ye gave me drink: I was a stranger, and ye took me in: Naked, and ye clothed me: I was sick, and ye visited me: I was in prison, and ye came unto me.
I reach this conclusion. Self-improvement is not spiritual, but living better is. Eating, sleeping, and exercising to mold myself into a stunning specimen of humanity may be great, but when used that way they are nothing spiritual. These same disciplines, however, when used to make me better able to love the people I love, seem pretty spiritual to me.
Food, rest, and work become the kingdom of God.