A farmer plows his field, sows the seed and fertilises and cultivates - all the while knowing that in the final analysis he is utterly dependent on forces outside of himself. He knows he cannot cause the seek to germinate, nor can he produce the rain and sunshine for growing and harvesting the crop. For a successful harvest, he is dependent on these things from God.
Yet the farmer knows that unless he diligently pursues his responsibilities to plow, plant, fertilise and cultivate, he cannot expect a harvest at the end of the season. In a sense he in in a partnership with God, and he will reap its benefits only when he has fulfilled his own responsibilities.
Farming is a joint venture between God and the farmer. The farmer cannot do what God must do, and God will not do what the farmer should do.
We say just as accurately that the pursuit of holiness is a joint venture between God and the Christian. No one can attain any degree of holiness without God working in his life, but just as surely no one will attain it without effort on his own part. God has made it possible for us to walk in holiness. But He has given to us the responsibility of doing the walking; he does not do that for us.
From the preface of The Pursuit of Holiness by Jerry Bridges.
And then in chapter three...
God does not require a perfect, sinless life to have fellowship with Him, but He does require that we be serious about holiness, that we grieve over sin in our lives instead of justifying it, and that we earnestly pursue holiness as a way of life.