“But how are we supposed to just change? you know, after God?”
Well, a day at a time, of course, but I try and think of it like this: what if, for that one day, a new christian was following your example? Would you be more conscience, then, of your behavior?

“Brothers, join in imitating me, and keep your eyes on those who walk according to the example you have in us.  For many of whom I have often told you and now tell you even with tears, walk as enemies of the cross of Christ. Their end is destruction, their god is their belly, and they glory in their shame, with minds set of earthly things.  But our citizenship is in heaven and from it we await a Savior, the Lord Jesus Christ, who will transform our lowly body to be like his glorious bod, by the power that enable him even to subject all things to himself.” Philippians 3:17-21

and what if I’m the example?
what if you are?
no one is perfect here, so we’re not pointing fingers. but Paul is saying here, “be careful- these people- they’re enemies of the cross, even those that are dressed to appear otherwise.”
What he is saying is that these people are destructive, self-serving, and even find a sense of pride in the very same things that one should be ashamed of.
The guy that brags about the number of girls he has slept with; the girl that thinks it’s cool that she can out drink the boys.
Paul is saying be careful and Jesus flat says no.

“Do not love the world or the things in the world.  If anyone loves the world, the love of the Father is not in him. For all that is in the world- the desires of the flesh and the desires of the eyes and the pride in life- is not of God but of world.” 1st John 2:15-16

you cannot love both.
There are some Christians that believe that since God is forgiveness, our souls can be saved and it just doesn’t matter what our bodies do; they’re wrong.
There are also Christians that believe that worldliness is limited to external behavior- you know, the people we hang out with, the places we go, the activities we enjoy and partake in, and y’all…. they’re also wrong.
Arguably even more wrong, even though that isn’t a thing, because they’re just dressing up the ugly underneath. Wordliness begins in the heart and is characterized by three attitudes: 1- desires of the flesh, preoccupation of gratifying physical desires 2- desire of the eyes, craving and accumulating things; idolizing materialism, even if on the inside and 3- pride of life- an obsession of status and importance.
The serpent tempted Eve with these things. (see genesis 3:6)
The devil tempted Jesus in the wilderness with these things. (see matthew 4:1-11)
and you better bet Satan is enticing you in these very same ways.
Even unintentionally, we’re so worried with our busy week that our minds wander on Sunday morning when the preacher speaks a sermon our hearts desperately need. We’re so preoccupied with planning our children’s activities, trying to maneuver how we can possibly shuffle all of these things into one elf-sized day, that we make no room for intentional prayer, maybe not even prayer at all. I’ve been guilty. And then all those activities that we’ve spilled over our calendars are leaking down the sides of what’s left of a mother when Thursday rolls around, and let’s be honest- there’s no time, certainly no energy, left for intimate time with Jesus and His word.
Satan is sifting through our lives, our schedules, and uncovering all of our leaks, our frailties and he is not only finding our holes, y’all, he is expanding them in a way that allows flaw to pour when flaw before, was just a trickle here and there.
As people of this world, we prioritize this world.
Again, I’m not blaming because Lord knows I am not perfect either..
Not perfect, but blameless.

“Even before he made the world, God loved us and chose us in Christ to be holy and blameless in his sight.” Ephesians 1:4

but this perfect? your own personalized portion of unperfect blamelessness… only comes from Jesus.

“who will transform our lowly body to be like his glorious body, by the power that enables him even to subject all things to himself.” philippians 3:21

Earlier in verse 18 of the text is says “I tell you with tears in my eyes.”
Paul cried.
Paul, the same man that was beaten on many occasions without a tear. Paul, the man that overcome so many obstacles quite literally running for his life so many times, again, without a tear. Paul, the man that sang praises to God while locked in a first century prison…. yet he cries for this people.
Why?
Because Paul knows that while all of this circumstance he has endured is temporary- a life of sin and unrepentance is not.
We cannot be both. Our conduct must match our citizenship and our character turn away from our culture.
what if, for that one day, a new christian was following your example?
Or maybe I should ask it this way: What if you knew Jesus were coming tomorrow? What would you change first? Your shoes or your heart?
It’s never going to be about things, about people, about status- when that day comes it’s only and always going to be about Him, your heart and how it knows Jesus.
Hugs,