Imagine grief as a ball inside a box, and on one side of the box is a button that causes you pain. As the grief ball bounces around the box it hits the button. The fresher or more intense the grief, the bigger the ball and the more often it hits the button.
Over time, the ball shrinks. It's still there and still bouncing around but it hits the button a little less often and with a little less less force. This shrinkage isn't linear; there will be big-ball days and there will be small-ball days, but the ball never leaves the box.