For the mind that is set on the flesh is hostile to God, for it does not submit to God's law; indeed, it cannot. Those who are in the flesh cannot please God.
As Christians, our ultimate purpose in life, death and after life is to worship - and therein please - God; it is the very summation of our human existence, and the highest completion of our joy. If then this is the peak of all our efforts, we should consider it a very grave and serious task to examine the manner in which we should attempt do this, and so we should be excited when we come across a passage that tell us how to better worship Him. Although these two verses are short, they tell us a great deal on how, or rather how not, to worship our great and awesome God.
Now, these verses tell us that if we want to please God, we absolutely cannot be in the flesh. But what does it really mean to be "in the flesh"?
Essentially, being in the flesh, or having your mind "set on the flesh" is focusing on all the distracting things that fill most of our days. Now, don't misunderstand here; not being in the flesh does not mean not doing all those tedious tasks that consume our daily lives; it means doing all those things with a higher task in mind. 1 Corinthians 10:31 says that everything we do, even the things that so insignificant as eating and drinking, should be done in worship to God. This means that the way to getting out of the mind of the flesh isn't by avoiding things that we view as pointless; it means making every little thing we do about God.
Now that we know that every task we do, from the most minute the the greatest, should be done in worship, one question still remains: How can we do all these things "for God"? Although I don't have a direct answer to this question I believe that the path to leaving the mindset of the flesh is by remembering and standing in awe of God in every moment. In other words, we should constantly be thinking about God, no matter what we're doing - just thinking about Him; what He's done, what He has yet to do, how we can please Him, etc. Some would call this obsession, and they'd be right, but God calls us to nothing less.
We so often fall into the mindset of the flesh not so often when we take a severe fall, but when we slowly and unrecognizably start to forget about God - He becomes a distant reality that we rarely think about. But if we truly want to be good God-worshipers, we have to beware - so aware - of remembering Him. And if we do that, and fix our eyes on Him, we're well on our way to true worship.