There are two reasons for this: first off, we are all creatures of habits. In fact, around 40% of what we do each day is simply habit. I would say that most of the ways we demonstrate (or not) our faith through actions are also habits. Moreover, the first step in changing a bad habit is the knowledge that it exists and monitoring it. So in pointing out habits that Christianity developed is part of the answer.
The other other key is contained in Philipians 3:
Not that I have already obtained all this, or have already arrived at my goal, but I press on to take hold of that for which Christ Jesus took hold of me. Brothers and sisters, I do not consider myself yet to have taken hold of it. But one thing I do: Forgetting what is behind and straining toward what is ahead, I press on toward the goal to win the prize for which God has called me heavenward in Christ Jesus.The word that is written here as "press on to take hold of" here is also translated strive.
The verb strive (diwkw) is used 24 times in the New Testament. It is used thirteen times in Matthew-Acts, always with the sense of to persecute or hunt down, as, for example, in the case of Israel who always persecuted the prophets sent to her (Matt 23:34; Acts 7:52). Paul uses the term ten times (Romans 9:30; 12:13, 14; 14:19; 1 Cor. 4:12; 14:1; 2 Cor 4:9; Gal 6:12; 1 Thess 5:15; 2 Tim 3:12), both in the sense of “to persecute” (Rom 12:14; 1 Cor 4:12; Gal 6:12; 2 Tim 3:12) and “to ardently pursue” something, i.e., righteousness (Rom 9:30); love (1 Cor 14:1); doing good to others (1 Thess 5:15). Whether Paul is thinking here of the athletic metaphor of running a foot race, as Hendriksen suggests, the point is clear: it is strenuous and requires great effort and focus.I think that this is a great word for us. Especially since, as we have seen in this book our tendency towards heresy can be out of wanting to make things easier. Or even to just decide that God wants us to be happy just the way we are. This is human nature. The challenge then is when we receive a word from God that is challenging to the place our hearts are in, either individually or collectively, we need to strive to move from that place. It will take effort and focus, intentionality and vulnerability, it may hurt or be embarrassing; but changing a heart is not easy business. And as Paul says, this is a continual striving. We will consistently be able to move more from our old selves towards Christ.