As one lives one's life, things assume a certain trajectory.  Life imparts a certain inertia - where the things that will happen, going forward, are pretty much determined by that which has happened in the past.  The future is, in some ways, predictable.

A guy works hard, he and his wife raise the kids and send them out into life, and then the guy and his wife sail off into the sunset life of retirement.  Predictable.

But it doesn't always go according to plan - Life throws things at you, once in a while, in a perverse effort to knock you off your nice, safe, pathway.

The trick, then, is to maintain your equilibrium and stay on your path, or, sometimes, find a new path that will lead to a similar end.  But standing and unbeaten.

That's the hard part.