"Flash powder makes a more brilliant light than the arc lamp, but you can't use it to light your street corner because it doesn't last long enough. Stability is more essential to success than brilliancy" (Richard Lloyd Jones).
IN THE LONG RUN, STABLE PEOPLE DO MORE GOOD IN THE WORLD THAN THOSE WHO'RE UNSTABLE. If we waffle and waver, we won't accomplish anything very significant, even though we have the best of intentions. As they say down South where I grew up, "Mean to" don't pick no cotton. So we need a good dose of stability added to our characters: we need to resist frivolous or unhelpful change, we need to be constant and steadfast in our purposes, and we need to be dependable enough that others won't hesitate to rely on us.
Intellectual stability. It's a fine thing to be open-minded. But our minds are like our mouths: we open them in order to close them on something solid. If after a lifetime of study, we still don't know anything for certain, then we've probably taken the wrong approach.
Volitional stability. Intellectual stability ought to lead to volitional stability, or stability of the will. At some point, we must become people who know how to make decisions and make them stick. A stable will is absolutely vital; without it, we can't keep commitments.
Emotional stability. Our feelings can be expected to fluctuate, and indeed, it would be a much less interesting world if they didn't. Nevertheless, we do need to be stable enough that our emotions don't overthrow our convictions or keep us in a constant state of doubt.
As you can see, all of the above are types of inward stability. This is, by far, the most important kind. "It is not the outward storms and stresses of life that defeat and disrupt personality, but its inner conflicts and miseries. If a man is happy and stable at heart, he can normally cope, even with zest, with difficulties that lie outside his personality" (J. B. Phillips). What we seek in life is not the absence of any storms that would batter us from the outside; we seek inward characters that are grounded in stable, trustworthy principles. And make no mistake: our principles are a matter of our own choice.
"Those who are the happiest are not necessarily those for whom life has been easiest. Emotional stability is an attitude. It is refusing to yield to depression and fear, even when black clouds float overhead. It is improving that which can be improved and accepting that which is inevitable" (James C. Dobson).