Learn Swedish: Du borde acceptera det ovissa och fokusera på det positiva. - You should accept the uncertain and focus on the positive.

In Swedish, you can turn an adjective into a noun by putting det in front of its definite form. This is very common for abstract concepts, so det ovissa means "the uncertain" or "uncertainty", and det positiva means "the positive". It often sounds more natural and idiomatic than using the equivalent nouns like ovissheten or positiviteten.

Why do ovissa and positiva end in -a if det is a neuter singular word?

Even though det is neuter singular, it acts as a standalone definite article here. Whenever an adjective has a definite article before it, it must take its definite form, which almost always ends in -a.

Why is the verb borde used here? Isn't that a past tense form?

Yes, borde is technically the past tense of böra (ought to). However, just like "should" in English, Swedish uses this past tense form to give advice or express a strong recommendation in the present or future. It softens the statement compared to a direct command.

Is the preposition på mandatory after fokusera in this sentence?