The principle Edwards is writing about is "Gracious and holy affections have their exercise and fruit in Christian practice."
The second and third implications are
That he(the Christian man) makes a business of such a holy practice above all things; that it be a business which he is chiefly engaged in, and devoted to, and pursues with highest earnestness and diligence; so that he may be said to make this practice of religion (Christianity) religion eminently his work and business. And, 3. That he persists in it to the end of life; so that it may be said, not only to be his business at certain seasons, the business of Sabbath days, or certain extraordinary times, or the business of a month, or a year, or of seven years, or his business under certain circumstances; but the business of his life; it being that business which he perseveres in through all changes, and under all trials as long as he lives.
pp. 308-309.
Religious Affections by Jonathan Edwards.
Note: Edwards further explains that Christian practice is obedience to the Word of God and holiness.