Life can never come a full circle as it has a linear relationship with time. The way I see it, life moves like a vortex. When it seems life has come around a full circle it is actually (and factually) displaced in time. So what seems like a point from the top view is actually a line in vertical plane.
If I were to construct an approximate model, time would be X-axis, life would be Y-axis and the displacement caused by the various external and internal factors would be Z-axis. You can be at the same place again but the time has moved and so have the external factors affecting the life. The image summarises it all.