The Advantage of Good Over Bad

Gemara: Never did a positive promise turn into something negative except …

Ein Ayah: Things have an intrinsic purpose in regard to their being a means of getting to a greater goal. It is intrinsically worthwhile to act toward the prospect of positive things. Negative things lack intrinsic value, although they have value for being an eventual conduit for the development of future good.
Considering Hashem’s attribute of goodness, only good things should be happening. On the other hand, the greatest good is the ethical good, which requires people to be fully good internally. Therefore, it is necessary for there to be real goodness and justice, so that man not only receive good but be good.
Since the goal is that there should be goodness in a broad manner, when Hashem pledges to provide something good, there is an expectation of two positive things: the coming of the good thing and preparation for an even better thing in the future. Sometimes a person’s circumstances change and the good that was foreseen as being able to provide future good no longer is destined to bring that state. Still, though, the positive pledge has value for its own sake, and Hashem can find other means to arrive at the ultimate good. Therefore, the direct good will still occur for its own intrinsic value. In this way, there is rationale for the rule that pledged good generally will continue to be kept, for its own sake, even when there is reason to suspend it.