Writing about 100 years ago, P. T. Forsyth reminds us about how true holiness is produced in us:
…if we are to produce the real Christian faith we must dwell upon, we must preach and press, that objective act and gift of God which in itself produces that faith.
We cannot produce it. Many try. There are some people who actually work at holiness. It is a dangerous thing to do, to work at your own holiness.
The way to cultivate the holiness of the New Testament is to cultivate the New Testament Christ, the interpretation of Christ in his cross, by his Spirit, which cannot but produce holiness, and a holiness of a far profounder order than anything we may make by taking ourselves to pieces and putting ourselves together in the best way we can (The Work of Christ, 71).
A comment, for what it’s worth: I don’t think he’s discarding effort altogether in the Christian life. Nor is he saying that we don’t have any work to do in pursuing our holiness. I assume he agrees with Hebrews 12:14: “Strive… for the holiness without which no one will see the Lord.” But he reminds us of the danger of bypassing affection for Christ and the cross in our pursuit of it. We don’t become holy ‘merely’ by trying hard to become holy, even though becoming holy will involve us intentionally, even vigorously, pursuing it. But seeing Christ and his grace to us in the cross will naturally (supernaturally) lead to a changed life. And out of that continually refreshed joy, all sorts of effort for holiness will arise.