Be but a little addicted to any one thing, and you are brought under the power of it. The flesh waxes wanton and imperious, and a slavery grows upon you by degrees. The more you cocker carnal affections, the more they increase upon you; and therefore you must hold the reins hard, exercise a powerful restraint. Solomon in his penitentials gives us an account of his own folly, and how fearfully he was corrupted this way: Eccles. 2:10, ‘Whatsoever mine eyes desired I kept not from them, I withheld not my heart from any joy,’ &c. This was that which brought him to such a lawless excess, and at length to fall off from God.
When we give nature the full swing, and use pleasure with too free a license, the heart is insensibly corrupted, and the necessities of life are turned into disease, and all that you do it is but in compliance with your lusts; your eating and drinking is but a meat-offering and drink-offering to lusts and carnal appetite. I remember Solomon saith, Prov. 29:21, ‘He that delicately bringeth up his servant from a child, shall have him become his son at length;’ i.e., allow a servant too much liberty, and he will no more know his condition, but grow contemptuous, bold, and troublesome; so it is here.
We are all the worse for license. Natural desires, unless they feel fetters and prudent restraints, grow unruly and excessive; and therefore it is good to abate the liberty of the flesh, that the body may be a servant and not a master. When you deny yourselves in nothing, but satisfy every vain appetite, custom grows upon the soul, and intemperance proves a trade and a habituated distemper, so that you cannot when you would, upon prudent and pious respects, refrain and command your desires; and therefore it is good sometimes to thwart and vex the flesh, as David poured out the water of Bethlehem that he longed for, 2 Sam. 23:17. Not to deny ourselves in what we affect and covet, lust grows into a wanton, and bold and imperious, and so prescribes upon us, and we are ‘brought under the power’ of these things.
-Thomas Manton, from his Farewell Sermon