When you talk of the vicissitudes of life, you're referring to the difficult times that we all go through: sickness, job loss, and other unwelcome episodes. No one can escape the vicissitudes of life.
While vicissitude comes from the Latin vicis , which means "change" and technically can mean a change of any kind, you'll find that vicissitude is almost always used to talk about an unfortunate event or circumstance. Losing a pet, crashing the car, being called in for jury duty: these are examples of vicissitudes — chapters in one's life that one would rather avoid but must get through. Some lives have more vicissitudes than others, to be sure, but no life is without events that test and challenge us.