If thou wouldst exercise thyself to godliness when thou art alone, guard thy heart against vain thoughts; this is the first work to be done, without which all that I have to commend to thee will be in vain. It is to no purpose to expect that a glass should be filled with costly wine, when it is filled already with puddle water. When the house beforehand was taken up by strangers, there was not room for Christ himself in the inn. If such flies be suffered and allowed in our hearts, they will spoil our best pots of ointment.

—George Swinnock
The Works of George Swinnock, 2:412-13.