Two commands sit side by side and the second one explains the first. Do not be conformed. Be transformed by the renewing of your mind.
Conforming is passive. Nobody decides to be conformed. It happens by proximity, gradually, through what you are around often enough to stop noticing. That is why it is dangerous. There is no moment where you agree to it.
So the counter is not more willpower. Paul does not say resist harder. He locates the change further upstream, in how you think, on the grounds that behavior follows thinking eventually.
Renewing is a process word. It is not a decision you make once and then possess. It suggests something that has to be done repeatedly because it keeps wearing off.
That is slower than we want and more honest than most advice. You are not going to think your way to a new life this week. You are going to feed your mind different material for long enough that it changes what feels normal.