Vicissitudes are the ups and downs of life — the changes that keep coming, some good but usually hard, that you did not choose and cannot stop. Money comes and goes, health comes and goes, a country is peaceful and then it is not. When you gather all of that together and speak of it as one thing, you can call it "the vicissitudes of life".

Two things make this word special. First, it is nearly always plural. You will see "vicissitudes", almost never "a vicissitude". Second, it almost always comes with "of": the vicissitudes of life, of war, of the market, of a long career, of fortune. It is one of those words that travels with a fixed set of friends.

It is a very formal word — you meet it in books, speeches, and serious articles, not in a talk with a friend. If your friend's shop closed, you would say "things have been hard for her", not "she has faced many vicissitudes". Using it in casual talk sounds either literary or slightly joking.

It also carries a certain feeling: quiet acceptance. The person who says it is usually looking back over a long stretch of time and saying, in effect, this is simply how life is — it turns, and you go on. That is why it fits so well after words like "through all the" and "despite the". It is not the word for one sharp shock; that is a blow or a disaster. It is the word for change that keeps happening, over years.

Though actually, it does not always mean bad things. Strictly it means change of any kind, and old writers use it that way — the vicissitudes of the seasons. But in modern English, when someone says it, they are nearly always thinking of trouble.