When the true light appears,
The entire planet turns to face it.
The summer solstice is the time of greatest light. It is a day of enormous power. The whole planet is turned fully to the brilliance of the sun.
This great culmination is not static or permanent. Indeed, solstice as a time of culmination is only a barely perceptible point. The sun appears to stand still. Its diurnal motion seems to nearly cease. Yesterday, it was still reaching this point; tomorrow, it will begin a new phase of its cycle.
Those who follow Tao celebrate this day to remind themselves of the cycles of existence. They remember that all cycles have a left and a right, an up side and a down side, a zenith and a nadir. Today, day far surpasses night, and yet night will gradually begin to reassert itself. All of life is cycles. All of life is balance.
So celebrate, but be not proud. For whenever you celebrate high achievement, the antithesis is also approaching. Likewise, in misfortune, be not sad. For whenever you mourn in grief, the antithesis is also approaching. Those who know how to reach the peak of any cycle and remain glorious are the wisest of all.