Learn Hardcore Portuguese (Portugal): Quando respiras de forma mais profunda, a mente acalma devagar. - When you breathe more deeply, the mind calms down slowly.

respiras = you breathe (informal tu, 2nd person singular)
respira can mean:
- he/she breathes (3rd person singular: ele/ela respira), or
- you breathe in the formal form (o senhor / a senhora respira).

This sentence is addressing someone informally, so it uses tu respiras (with the tu left out, which is very common). If it were formal, it would be Quando respira de forma mais profunda….

Where is the word you in this sentence?

Portuguese normally drops subject pronouns when the verb ending already shows who the subject is.

The ending -as in respiras clearly marks tu (informal you).
So the full version would be Quando tu respiras de forma mais profunda…, but the tu is omitted.

English needs the subject pronoun you, but Portuguese often leaves it out because the verb form itself carries that information.

Why is the present tense respiras used with quando if we’re talking about a general effect or future situation?

In Portuguese, the present indicative with quando often expresses:

general truths or habits:
- Quando respiras de forma mais profunda, a mente acalma devagar.
  (Whenever / When you breathe more deeply, the mind slowly calms down.)
future situations that are seen as certain or regular:
- Quando chegas a casa, liga-me.
  (When you get home, call me.)

English often uses the present too in these cases, so the logic is actually similar: When you breathe more deeply, the mind calms down…

Could we use a future form like quando respirares instead of quando respiras?

Yes, but it slightly changes the focus:

Quando respiras de forma mais profunda…
Sounds like a general rule or typical effect: When(ever) you breathe more deeply…
Quando respirares de forma mais profunda…
Uses the future subjunctive (respirares) and tends to sound more like a specific future event or instruction:
When you breathe more deeply (in that future situation)…

In everyday speech about a general principle, quando respiras is more natural.

What exactly does de forma mais profunda mean, and why is it used instead of just profunda?

forma = form / way / manner
de forma ≈ in a … way / in a … manner
mais profunda = deeper / more deep

So de forma mais profunda literally means “in a deeper way”, which corresponds to the English adverb “more deeply”.

You can’t just say profunda by itself here, because that’s an adjective, and you need an adverbial idea (how you breathe). Portuguese often uses:

de forma + adjective → adverbial phrase
- de forma profunda = deeply
- de forma mais profunda = more deeply

Could we say mais profundamente instead of de forma mais profunda?

Yes:

Quando respiras mais profundamente…
Quando respiras de forma mais profunda…

Both are correct and natural. Differences:

mais profundamente:
- simple, direct adverb from profundo → profundamente
- slightly more compact
de forma mais profunda:
- literally in a deeper way
- very common structure, slightly more “spelled out”

In everyday speech, many people would actually prefer mais profundamente or even mais fundo (more deeply in a more colloquial way).

Is forma necessary, or can I drop it and just say Quando respiras mais profunda?

You cannot say mais profunda by itself after respiras:

profunda is an adjective and must describe a noun:
- uma respiração profunda = a deep breath
After respiras, you need something that functions like an adverb (tells you how you breathe):

Correct options:

Quando respiras mais profundamente…
Quando respiras de forma profunda…
Quando respiras de forma mais profunda…
Quando respiras mais fundo… (more colloquial)

So you either use de forma + adjective or an adverb form like profundamente / mais profundamente.

Why is it a mente and not just mente?

Portuguese often uses the definite article (o / a / os / as) with abstract or general nouns, where English uses no article:

a mente = literally the mind, but often translates as just mind.
a saúde = health
a vida = life

So:

a mente acalma devagar ≈ the mind calms down slowly / the mind becomes calm slowly.

Leaving out the article (mente acalma devagar) is unusual here and would sound incomplete or wrong.

Why isn’t it a tua mente (your mind)?

It could be:

Quando respiras de forma mais profunda, a tua mente acalma devagar.

Differences:

a mente (without possessive) is more general / universal:
the mind in general (anyone’s mind) calms down when you breathe deeply.
a tua mente focuses specifically on your mind.

In Portuguese, when the context is clearly about the person being addressed, it’s common not to repeat the possessive if it’s obvious:

Fecha os olhos. = Close your eyes. (literally “the eyes”)
Relaxar o corpo. = Relax your body.

Should acalma be acalma-se? Is something missing?

Both are possible, with a subtle difference:

a mente acalma devagar
- acalmar is used here as an intransitive verb: the mind calms (down) slowly.
- Grammatically fine and idiomatic.
a mente acalma-se devagar
- Reflexive form (literally: the mind calms itself slowly).
- Also correct and very common; many speakers might naturally choose this.

In this sentence, both versions sound natural in European Portuguese. The non-reflexive acalma is slightly more concise; acalma-se can feel a bit more “self-contained” or reflexive in meaning.

What does devagar mean, and could it go somewhere else in the sentence?

devagar means “slowly”.

Word order:

Normal and very natural here:
- a mente acalma devagar.

Other correct options (slightly different emphasis):

a mente devagar acalma – technically possible but sounds poetic or marked.
devagar, a mente acalma – starting with the adverb for emphasis, e.g. in meditation-style language: slowly, the mind calms…

Most natural in everyday speech and writing is exactly as given: a mente acalma devagar.

You can also replace devagar with lentamente (also slowly), which is a bit more formal or neutral:

a mente acalma lentamente.

Is this sentence specifically European Portuguese? How would Brazilians usually say it?

The sentence as given is neutral enough that Brazilians will understand it perfectly, but for typical Brazilian Portuguese you’d more often see:

Quando você respira mais profundamente, a mente se acalma devagar.

Changes:

você respira instead of (tu) respiras (Brazilian Portuguese usually uses você as the default you).
se acalma instead of acalma or acalma-se (in Brazil, the reflexive pronoun usually comes before the verb in speech and informal writing).
mais profundamente instead of de forma mais profunda is probably more common in conversation, though de forma mais profunda is also correct.