Why does God allow us to suffer?
J. I. Packer puts Thomas Boston squarely within the realm of the Puritans, and reading this work you can see why. The Evangelical spirit and the desire for humble submission and a holy life before Christ in God is evident throughout. Boston encourages us to see our afflictions, the "crooks" in our "lot" as part of God's divine plan. To see the good in the thorns of the flesh that God has deemed us worthy of in this dispensation.
"A just view of afflicting incidents is altogether necessary to a Christian deportment under them: and that view is to be obtained only by faith, not by sense. For it is the light of the word alone that represents them justly, discovering in them the work of God, and consequently designs becoming the divine perfections. These perceived by the eye of faith, and duly considered, one has a just view of afflicting incidents, fitted to quell the turbulent motions of corrupt affections under dismal outward appearances.
Consider the work of God: for who can make that straight which he hath made crooked? (Ecclesiastes 7:13)
In which words are proposed, (1.) The remedy itself, (2.) The suitableness thereof. First, The remedy itself is a wise eying the hand of God in all we find to bear hard upon us: Consider the work (or, See thou the doing) of God, to wit, in the crooked, rough, and disagreeable parts of thy lot, the crosses thou findest in it. Thou seest very well the cross itself; yea thou turnest it over and over in thy mind, and leisurely views it on all sides; thou lookest withal to this and the other second cause of it; and so thou art in a foam and fret: but, wouldst thou be quieted and satisfied in the matter, lift up thine eyes toward heaven, see the doing of God in it, the operation of his hand: look at that, and consider it well; eye the first cause of the crook in thy lot, behold how it is the work of God, his doing. Secondly, As for the suitableness of this remedy, that view of the crook in our lot is very suitable to still indecent risings of heart, and quiet us under it: for who can (that is, none can) make that straight which God hath made crooked? As to the crook in thy lot, God hath made it; and it must continue while he will have it so. Shouldst thou ply thine utmost force to even it, or make it straight, thine attempt will be vain: it will not alter for all thou canst do, only he who made it can mend it, or make it straight. This consideration, this view of the matter, is a proper means, at once to silence and satisfy men, and so to bring them unto a dutiful submission to their Maker and Governor, under the crook in their lot."