I think one of the greatest lessons we can learn is that of the transient nature of our affections and the deep necessity of plain perseverance. Henry Ware Jr. makes the point in this continuation of "Progress of the Christian Life:"
"There are also some mistaken notions respecting religion itself which may lead to the same error; the idea, namely, which so readily finds a welcome in the mind which is glowing with the first happiness of its early faith, that its glow cannot fade away; that things will always appear to the soul just as they do at that divine moment,- that the new taste is fixed, and cannot be changed; that it will take care of itself. Hazardous and unfounded as such a feeling is, it is yet very natural. It belongs to all strong emotion to have faith in its own perpetuity. The affections always are confident that they never shall change; and we always fancy that the grief, or love, or indignation, which fills our bosoms now, can never fade from them...
This is the conviction which occasions the well-known confidence and presumption of young converts, which prompts to their proverbial forwardness — a confidence and forwardness often attributed to unworthy motives, and spoken of to their discredit. It may not be creditable to them; yet it argues nothing worse, perhaps, than self-ignorance. They do not know the evanescent character of the feelings, the deceitfulness of the heart ; therefore they give way to it; they trust themselves; they spread all their sails to the wind, as if it would never change; they fancy themselves established, and act warmly and boldly, as if established. But this glow is necessarily transient, like all vehement feeling ; and when it has passed away, they have no abiding principle of life to take its place and keep the work in progress. Other feelings rise up in the midst of the world; the brightness of the spiritual light fades from before the eye of the soul, and there is no advancement to a higher perfection.
Let no one, therefore, from the strength and security of his first affections, allow himself to rest, as if the work were done. It is but begun. Let him settle within himself, deeply and sternly, the persuasion that it is to be going on while life lasts. For want of this it is that the love of so many has waxed cold, and that so many who put their hand to the plough have turned back. If you would persevere, you must understand, at the outset, the necessity of perseverance. You must start with the conviction that you begin a perpetual progress."