Galatians 5 makes it pretty plain that we are in a battle everyday-the battle of our sinful nature and the Spirit. It creates conflict in us and sometimes (far too often if you ask me) makes for very difficult days. They are in opposition to each other and cannot coexist peacefully.
Anyone who intends to feed both animals and expect to do so successfully is only fooling themselves. It has to be an honest effort (although that effort will most definitely be futile if attempted by our own willpower and strength) to do the things that lead to a Spirit-filled life. It's obvious throughout Scripture that what we put our efforts into, talk about, think about, watch, listen to, dwell on and act on will influence what we end up as. If a Spirit-filled life is what we intend to have then there must be a desire and an effort on our part to end up there. You don't "accidentally" become Spirit-filled. You choose now which team you will be on and then we trust in a God who wants to make His strength evident in our weaknesses. As He works in our willing spirits we will see the godly results He desires for our lives.
"But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self-control. Against such things there is no law." Galatians 5:22-23