Ebbing and flowing describes a repeated decline and rise, like the motion of the tides. It often refers to changing moods, energy, trends, or conversation that grows quiet, then lively again.
These were the rhythms of his life: indifference and violence; periods of abstract brooding and periods of intense desire; moments of silence and moments of anger- like water ebbing and flowing from the tug of a far-away, invisible force. Richard Wright
There were long stretches where each of us was engaged in a private world of rapidly shifting vignettes. Always I was overwhelmed by the sheer number of human beings ebbing and flowing like the tides of the sea. Howard Thurman