The next sentence of "The quiet years are no match for the fleeting years" is: A heart as solid as a rock is no match for the fleeting clouds.

It means: Time is quiet and beautiful, but it cannot withstand the torrent of time. No matter how firm your heart is like an unshakable rock, in the end it is just a cloud of smoke drifting past your eyes. Disappeared.

These two sentences come from Wang Xiaobo's work "Homecoming". This book introduces that Homecoming is everything a person has, and only this thing truly belongs to you. Everything else is a moment of joy and misfortune, and in the blink of an eye, it has gone by in the past.