Learn Hardcore Dutch: Haar motivatie is hoog, maar zijn motivatie is soms laag als hij moe is. - Her motivation is high, but his motivation is sometimes low when he is tired.

Haar motivatie is hoog.
→ haar is followed by a noun that she possesses (motivatie) → means her.
Haar haar is lang.
→ first Haar = her, second haar = hair.
Her hair is long.

So in Haar motivatie is hoog, the only logical reading is her motivation is high.

Why do we say haar motivatie and zijn motivatie instead of de motivatie van haar / hem?

Both structures are possible, but they feel different:

haar motivatie / zijn motivatie
= natural, neutral way to say her/his motivation.
de motivatie van haar / hem
= more emphatic or contrastive; often used when you really want to stress who it belongs to.

Examples:

Haar motivatie is hoog. (normal)
De motivatie van haar is hoog, niet de motivatie van hem.
(stronger contrast: HER motivation is high, not HIS.)

In everyday speech, the possessive adjectives haar / zijn are much more common than van + pronoun here.

Why is it hoog and laag, not hoge and lage?

Dutch adjectives behave differently depending on where they appear:

Predicative position (after a verb like is, zijn, lijken):
→ usually no -e ending.

Haar motivatie is hoog.
Zijn motivatie is soms laag.

Attributive position (directly before a noun with its article):
→ usually with -e.

haar hoge motivatie
zijn lage motivatie

So in your sentence, the adjectives are in predicative position (motivatie is hoog / laag), so they stay hoog / laag, without -e.

Could I also say haar hoge motivatie or zijn lage motivatie?

Yes, but you have to change the structure of the sentence slightly.

Haar motivatie is hoog.
= Her motivation is high. (adjective after is)
Haar hoge motivatie helpt haar om door te gaan.
= Her high motivation helps her to keep going. (adjective directly before motivatie)

Similarly with laag:

Zijn motivatie is soms laag als hij moe is.
Zijn lage motivatie maakt het soms moeilijk als hij moe is.
(His low motivation makes it difficult sometimes when he is tired.)

So:

is hoog / is laag → predicative
hoge motivatie / lage motivatie → attributive

What exactly does soms mean, and where can it go in the sentence?

soms means sometimes.

Typical positions in a main clause:

after the finite verb:
Zijn motivatie is soms laag.
at the very beginning, for emphasis:
Soms is zijn motivatie laag.

Both are correct. The difference is emphasis:

Zijn motivatie is soms laag…
→ neutral.
Soms is zijn motivatie laag…
→ puts more focus on “sometimes”.

In your sentence, … is soms laag als hij moe is is a very natural word order.

Why is the verb at the end in als hij moe is?

als hij moe is is a subordinate clause (it starts with a subordinating conjunction: als).

In Dutch subordinate clauses, the finite verb usually goes to the end:

hij is moe (main clause word order: Subject – Verb – Other)
als hij moe is (subordinate: Subordinator – Subject – Other – Verb)

So:

Main clause: Zijn motivatie is soms laag…
Subordinate clause: … als hij moe is.

This verb-final rule is one of the most important word-order rules to learn for Dutch.

What’s the difference between als hij moe is and wanneer hij moe is?

Both can often be translated as when he is tired, but there are tendencies:

als
- very common in spoken Dutch
- used for repeated or real situations in the present/past
- can also mean if in conditional sentences
wanneer
- feels a bit more formal or written in many contexts
- often used when you talk about specific points in time, plans, schedules, etc.

In your sentence:

… zijn motivatie is soms laag als hij moe is.
= completely natural, everyday Dutch.

You could say wanneer hij moe is, but als is more typical in casual speech here.

In zijn motivatie, is zijn the same word as the verb zijn (“to be”)?

They look the same in spelling, but they are different words:

zijn (possessive adjective) = his

zijn motivatie = his motivation
zijn auto = his car

zijn (verb to be, infinitive) and is (3rd person singular present):

Hij is moe. = He is tired.
Ik wil gezond zijn. = I want to be healthy.

In your sentence:

zijn motivatie → zijn = possessive (his)
… als hij moe is. → is = verb (is)

Can we avoid repeating motivatie and say something like maar de zijne is soms laag?

Yes, you can, and that’s good, natural Dutch:

Haar motivatie is hoog, maar de zijne is soms laag als hij moe is.
= Her motivation is high, but his is sometimes low when he is tired.

Here:

de zijne = his (one), referring back to motivatie.
You need de because motivatie is a de-word.

This sounds a bit more stylistically polished than repeating motivatie, but repeating it (as in your original sentence) is also perfectly correct and very clear.

Is motivatie a de-word or a het-word, and does that matter here?

motivatie is a de-word:

de motivatie

In this particular sentence, it doesn’t visibly affect anything, because:

The adjective is predicative (is hoog / is laag), so no -e issue.
The possessives haar and zijn don’t change form based on de/het.

It does matter in related structures, for example:

de hoge motivatie (not het hoge motivatie)
de hare / de zijne when you replace the noun:
- Haar motivatie is hoog, de hare is erg sterk.
- Zijn motivatie is laag, de zijne is niet zo sterk.

How do you pronounce motivatie, and where is the stress?

motivatie is pronounced roughly like:

/moː.tiˈvaː.tsi/
In English-like approximation: moh-tee-VAH-tsie

Details:

mo = like mow (as in mow the lawn), but the o is long.
ti = like tee.
va = like vah with an open a.
tie = like tsee.

The stress is on the third syllable: mo-ti-VÁ-tie.