Happiness is a choice

Mill also said “I have learned to seek my happiness by limiting my desires, rather than in attempting to satisfy them.” 

I'm ambivalent about that. Of course the Stoic knows what he knows, the world spins on its own axis (not yours or mine), and the satisfaction of desire is often enough out of reach to make this sound like simple good sense. The Sisyphean laborer only compounds his injury with unrealistic desires. The prisoner only magnifies his captivity by pining for immediate release.

But where's the joy in this conception of happiness-as-compromise? Why merely settle?

I prefer the position James starts from in "Moral Philosopher and Moral Life":

The only possible reason there can be why any phenomenon ought to exist is that such a phenomenon actually is desired. Any desire is imperative to the extent of its amount; it makes itself valid by the fact that it exists at all. Some desires, truly enough, are small desires; they are put forward by insignificant persons, and we customarily make light of the obligations which they bring.  But the fact that such personal demands as these impose small obligations does not keep the largest obligations from being personal demands.

In other words, don't trim your desires until you have to. Begin with great expectations. Go out and conquer happiness. Realize too that one person's small desire is someone else's joy. "Hands off!"

But recognize that you're not the only seeker out there, not the only castaway on the island. You must be prepared to compromise. Our happiness sometimes consists in the strategic limitation of some of your desires, and mine, in order that the greatest number and quality of them may eventually be met.

Every end of desire that presents itself appears exclusive of some other end of desire. Shall a man drink and smoke, or keep his nerves in condition?‑-he cannot do both. Shall he follow his fancy for Amelia, or for Henrietta?‑-both cannot be the choice of his heart.

Well, that last may be the Age of Victoria speaking. (And it's probably true.) But we do get James's point, don't we? Happiness is always a choice. But it's also always a stimulant, not an anaesthetic.  It's an expansion of the heart's desires, or more precisely the hearts'...  not their constriction. We don't have to settle.