Learn Hardcore Spanish (Spain): Al comienzo del día quiero respirar hondo y mantener la calma. - At the beginning of the day I want to take a deep breath and stay calm.

You can say en el comienzo del día, but it sounds heavier and less natural in everyday speech. In time expressions, Spanish normally prefers a / al (or no preposition) rather than en:

Al final del día (most natural)
En el final del día (grammatical, but clunky / very marked)

So al comienzo del día is the idiomatic choice for “at the beginning of the day.”

What is the difference between al comienzo del día and al principio del día?

They’re very close in meaning and often interchangeable:

al comienzo del día – “at the start of the day”
al principio del día – “at the beginning of the day”

Nuances (quite subtle):

comienzo is a bit more “event-like,” focusing on the act of starting.
principio can sound a bit more abstract or structural (the first part of something).

In practice, most speakers won’t feel a real difference here. Both are fine in this sentence.

Why do we say del día and not just de día or de un día?

del día = de + el día = “of the day.”
Here, Spanish uses the definite article el to talk about the generic day we are in, very much like English the in at the end of the day.
de día usually means “in the daytime” (as opposed to at night):
- Trabajo de día y estudio de noche. – “I work by day and study at night.”
de un día would sound like “of a (certain) day,” referring to some unspecified day, and it wouldn’t fit the habitual, general meaning here.

So al comienzo del día is the set phrase for this idea of “at the start of the (every) day.”

Why is there a contraction al and del?

Spanish always contracts a + el → al, and de + el → del:

a + el comienzo → al comienzo
de + el día → del día

You cannot say a el comienzo or de el día; that’s considered incorrect. With la there’s no contraction:

a la noche (not al noche)
de la mañana (not del mañana, unless you mean “of tomorrow”).

Why is it quiero respirar and not quiero que respiro or quiero que respire?

In Spanish, when both verbs have the same subject, the second verb is normally in the infinitive:

(Yo) quiero respirar hondo. – “I want to breathe deeply.”
(Subject of quiero and respirar is the same: yo.)

You use quiero que + subjunctive when the subject changes:

Quiero que tú respires hondo. – “I want you to breathe deeply.”
Quiero que él respire hondo. – “I want him to breathe deeply.”

Quiero que respiro is ungrammatical. With querer + que, the following verb must be in the subjunctive (respire, respires, etc.), and it signals that someone else is doing the second action.

Why isn’t yo written before quiero?

Spanish normally drops subject pronouns when the verb ending already shows who the subject is:

quiero → the -o ending tells you it’s yo.
quieres → tells you it’s tú.
queremos → tells you it’s nosotros.

So (Yo) quiero respirar hondo… is understood as “I want to breathe deeply…” even without yo.

You add yo only for emphasis or contrast:

Yo quiero respirar hondo, pero tú quieres salir corriendo.
“I want to breathe deeply, but you want to run away.”

In respirar hondo, what exactly is hondo and why isn’t it profundamente?

Hondo is an adjective meaning “deep,” but in respirar hondo it works like an adverb, describing how you breathe: “to breathe deeply.”

You can also say:

respirar profundamente – literally “to breathe profoundly / deeply.”

Differences:

respirar hondo is very common and slightly more colloquial / everyday.
respirar profundamente is equally correct, perhaps a touch more formal or neutral.

Native speakers use both; respirar hondo is probably the most idiomatic-sounding in this exact sentence.

Is there any difference in meaning between respirar hondo and respirar profundamente?

In real usage, almost none: both are understood as “breathe deeply.”

Very small nuance:

respirar hondo feels a bit more like a simple physical action: a deep breath.
respirar profundamente can sound just a bit more formal or slightly more “serious”/emotional in some contexts.

But they are interchangeable in this sentence, and choosing one or the other doesn’t change the message.

Why is it mantener la calma and not mantener calma?

Spanish often uses a definite article + noun where English might use a bare noun or an abstract noun without the.

mantener la calma literally = “to maintain the calm,” but it means “to keep calm / stay calm.”
Saying mantener calma is possible but feels incomplete or less idiomatic here; native speakers almost always say mantener la calma.

This is a fixed expression:

Mantén la calma. – “Keep calm.”

The pattern appears in similar phrases:

perder la paciencia – “to lose patience”
guardar la calma – “to keep calm”

So the article la is just part of the natural idiom.

Why is calma a noun here and not an adjective like calmado?

There are two common ways to express this idea:

With a noun:
- mantener la calma – literally “to maintain the calm.”
  This is a set phrase.
With an adjective + verb “estar”:
- estar calmado / tranquilo – “to be calm.”

Your sentence uses structure (1), which focuses on maintaining a state (the calmness itself) rather than describing yourself with an adjective. Both structures are common, but mantener la calma is the idiomatic, ready-made expression for “keep calm.”

Why are respirar and mantener both in the infinitive and joined just by y?

After querer, when the subject is the same for all the actions, all the following verbs stay in the infinitive:

Quiero respirar hondo y mantener la calma.
→ I (yo) want [to breathe deeply] and [to keep calm].

You don’t need to repeat quiero:

Not necessary: Quiero respirar hondo y quiero mantener la calma.
(Still correct, but heavier and more emphatic.)

This is very common:

Quiero comer y dormir. – “I want to eat and sleep.”
Necesito descansar y relajarme. – “I need to rest and relax.”

Could I move al comienzo del día to another part of the sentence?

Yes. Common options (all correct, slightly different emphasis):

Al comienzo del día quiero respirar hondo y mantener la calma.
(Time expression first; sets the scene.)
Quiero, al comienzo del día, respirar hondo y mantener la calma.
(More marked; commas make it a parenthetical remark.)
Quiero respirar hondo y mantener la calma al comienzo del día.
(Puts more focus on the actions, then specifies when.)

All three are grammatical. The version you gave is very natural and neutral.

Why does día have an accent on the í?

In día we have two vowels together: í (weak) + a (strong). Normally those would form one syllable (dya), but Spanish pronounces this word as two syllables: dí‑a.

When a weak vowel (i, u) is stressed and forms its own syllable next to another vowel, Spanish marks it with an accent to show there is a hiatus (two separate syllables), not a diphthong:

día → dí‑a
frío → frí‑o
río → rí‑o

So the accent on día is there to show both pronunciation (two syllables) and stress (on dí).