who can express the state of having already attained the ineffable?

Perfect joy excludes even the very feeling of joy, for in the soul filled by the object no corner is left for saying 'I'. We cannot imagine such joys when they are absent, thus the incentive for seeking them is lacking.

When we have attained success, we see how inferior it is to the hope, yearning and enthusiasm with which we started forth in life’s morning.

Is there anything in life so disenchanting as attainment?

"Happiness is simply the absence of desire. When you observe a cue, but do not desire to change your state, you are content with the current situation. Happiness is not about the achievement of pleasure (which is joy or satisfaction), but about the lack of desire. It arrives when you have no urge to feel differently. Happiness is the state you enter when you no longer want to change your state.
However, happiness is fleeting because a new desire always comes along. As Caed Budris says, “Happiness is the space between one desire being fulfilled and a new desire forming." Likewise, suffering is the space between craving a change in state and getting it.

Comparison is the death of joy.

Comparison is the death of joy.

"Sorrow can only be compared with the memory of joy, which is not at all the same thing as joy itself. Like words, memories never really succeed in "catching" reality."

Happiness is the abscence of the striving for happiness.

Achievement is the death of endeavor and the birth of disgust.

Happiness is a state of nonillusion, of dropping the illusion.

The joy of having something comes from the length of time you have been wanting it, expecting it. Happiness really lies in the expectation. So once you achieve it, it loses its charm for you. Every happiness is imaginary: so long as you don’t possess it, it seems to be abounding happiness. But as soon as it is actualized, it ceases to be happiness; our hands are as empty as before. And then we seek some other object for our desire, and we begin to expect it again. We feel so unhappy without it and imagine that happiness will come with it.

We can't wait to be happy until we remove one hundred percent of suffering. That moment will never exist.

Mark Twain nailed it: “Comparison is the death of joy.” We’re with Mark.