Learn Italian: Queste cose capitano: non è colpa tua. - These things happen: it is not your fault.

It comes from capitare, which means to happen or to occur. It is a regular -are verb, so the "they" form used for Queste cose (these things) is capitano.

Why isn't there an article before colpa tua? Shouldn't it be la tua colpa?

Usually, possessive adjectives need a definite article in front of them. However, in the very common phrase è colpa tua (it's your fault) or è colpa mia (it's my fault), the article is dropped. This is a set expression you will hear constantly when using the verb essere to assign or remove blame.

Why does tua come after colpa instead of before it?

While possessives normally go before the noun, putting the possessive after the noun in phrases like è colpa tua is simply the natural, idiomatic way Italians express this specific idea. Placing it at the end also adds a tiny bit of emphasis to who is (or isn't) at fault.

How would I apply this lesson's grammar to say "These things COULD have happened"?