I remember a few years ago my mentor saying that as she learned to discipline her body through exercise that the discipline rolled over into the spiritual disciplines of reading the Word, prayer, etc.
There is a connection between your natural life that you live in the flesh and the things of the Spirit. One of the many things that our awesome Holy Spirit, our Counselor, does is lead us and guide us to bring the flesh into submission of the Kingdom of God.
Paul said it well in 1 Corinthians 9:27, "But I discipline my body and keep it under control..."
One of the many purposes of the Spirit inside of you is that He disciplines your flesh. To put it matter of factly, if you truly have a relationship with the Spirit of the living God then your flesh will begin to change. It will begin to sound different, act different, think different, instead of being selfish it will be sacrificed, instead of being prideful it will be humble, instead of being angry it will be peaceful. The Spirit will put you on a continual journey of sanctification to put the flesh into submission and make you be more like Jesus Christ.
I've always liked the illustration of feeding the dogs. If one dog is my Spirit and one dog is my flesh, the one that I feed more is the one that will grow more inside of me. The more that I submit to Spirit's guidance the more my flesh dies and He arises inside of me (He must increase, I must decrease). The more I give in to my flesh then the more I look like the world.
I've learned that there is a huge connection between discipling my flesh in natural ways and growing in the Spirit. It is wise to see that connection and deny your flesh its desires even in things that seem insignificant. Here's a few simple things.
1. Don't always eat the cookie. Is there anything wrong with eating a cookie? Nope. Not at all. However, your flesh likes cookies. Your flesh likes cheeseburgers. No matter how skinny or not skinny you are is insignificant. Make it a point to tell your flesh no, rather than it telling you what to do. You tell it what to do.
2. Do the extra and go lower still. I try to practice this one daily and it's still the one I have the hardest time with. When your flesh says "okay you're done", or "that's not necessary". You tell your flesh who controls you. This can take many forms from parking at the back of a parking lot so that others can have the close spots, to running an extra mile than I had planned, to reading an extra chapter in the Word, to picking up the trash you see on the floor, opening the door for someone, giving 100% effort even when no one is watching. This one will take a lifetime of practice, but I'm convinced as my 8th grade english teacher always said, "character is what you are in the dark". Who am I when no one is watching?
3. Don't hit the snooze button. (Thank you Kayce Strader) A few years ago my wise friend decided she would no longer hit the snooze button. I remember her saying this one phrase "I decided I didn't want to be the type of person who snoozes". Is there anything wrong with the snooze button? Absolutely not. But it's one way your flesh gets to tell you what it's going to do. Just get out of bed, if you fall back asleep on the couch, at least you made it get out of bed.
It cannot go unnoticed in scripture that when we yield to Him, our Holy Spirit, our flesh looks different. It says over and over and over "walk in the Spirit", the deeds of the flesh are... the deeds of the Spirit are... If you walk in the Spirit you...
Yielding is in discipline and submission. Discipline your flesh and submit to your Spirit.
"If we say we have fellowship with him while we walk in darkness, we lie and do not practice the truth." (1 John 1:6)