ebb and flow

ebb and flow

noun. and verb.  (1) (of tide water) outgoing and incoming phase; (2) a decline and increase;  constant fluctuations

"The stock market tends to ebb and flow. When the market is not doing well, investors needs to be patient to leave their funds long enough to recoup, or better yet, grow investments."

"New York Giants running back Shane Vereen looks central to New York's game plan one week then he is absent the next. An ESPN article tries to answer why his role will ebb and flow."

"She is fascinated by the ebb and flow of the Church's influence over the centuries. "