Hebrews 9:23
How then (he says) did you say that willing is sufficient? [I meant] willing joined with deeds, the laying hold on the thing itself, the laboring. For we have God working with us, and acting with us. Only let us make our choice, only let us apply ourselves to the matter as to work, only let us think earnestly about it, only let us lay it to heart, and all follows. But if we sleep on, and as we snore expect to enter into heaven, how shall we be able to obtain the heavenly inheritance?
Let us therefore be willing, I exhort you, let us be willing. Why do we carry on all our traffic with reference to the present life, which tomorrow we shall leave? Let us choose then that Virtue which will suffice us through all eternity: wherein we shall be continually, and shall enjoy the everlasting good things; which may we all attain, in Christ Jesus our Lord, with whom to the Father together with the Holy Ghost be glory, power, honor, now and for ever and world without end. Amen.
Source: Homilies on the Epistle to the Hebrews (New Advent)