John Preston (1587-1628), in The Breast-plate of Faith and Love, says,
So it is with the Lord, though there be many thousands that God loves, yet every one hath the Lord wholly, he is to them alone, and expect thee to be to him alone, to bestow thyself wholly on him. Thereupon all those words are put in, Thou shalt love the Lord with all thy mind, with all they heart, with all thy soul.
The meaning is this, when all that is in a man is set on work to serve the Lord, when he looks to the Lord, when he inclines towards the Lord, that is, when the mind is set on work to think on him, to remember his glorious works, to have a right knowledge and opinion of him–again, when the memory is set on work to remember him, and not to forget his benefits, his statutes and his ordinances, and so the rest of his faculties.
And therefore if we love the Lord, we will not do this with ourselves, to think I love him, and yet I will suffer my mind in the mean time, to be exercised in contemplating of fornication; nor to think I love the Lord, and yet will suffer my memory in the mean time, to be recollecting injuries and breeding of them, and recalling my pleasant sins that are formerly past, that I should abhor, thou canst not love him and do this.
Again, thou must not say I love him, and yet let thy affections run after this and that, but thy whole heart must be bestowed on him. Thou must not think to love him and to serve thy affections for this or that particular thing that thou lovest inordinately, but must bestow all these on the Lord.