No es tu culpa si estás cansada; nadie es capaz de trabajar bien sin descanso.

Spanish uses estar for temporary states or conditions and ser for inherent characteristics.

• Estar cansada = to be tired right now / at this time (a condition that changes).
• Ser cansada is rare and would mean something like “to be a tiring person” (as a characteristic), not “to feel tired.”

So “si estás cansada” correctly talks about your current state of being tired.

Adjectives in Spanish agree with the gender and number of the person they describe.

• Cansada = feminine singular (talking to a woman).
• Cansado = masculine singular (talking to a man).

So:

• To a woman: No es tu culpa si estás cansada.
• To a man: No es tu culpa si estás cansado.

Everything else in the sentence stays the same.

Both are correct; they’re just two different but common structures:

1. No es tu culpa

   • Literally: “It is not your fault.”
   • Structure: possessive adjective + noun.
   • Very direct and common.

2. No es culpa tuya

   • Literally: “It is not fault of yours.”
   • Structure: noun + stressed possessive adjective.
   • Slightly more emphatic or conversational.

In meaning, they’re basically the same in this context.

• tu (without accent) = possessive adjective: your

  • tu culpa = your fault
  • tu casa = your house

• tú (with accent) = subject pronoun: you (informal singular)

  • Tú estás cansada. = You are tired.

In the sentence, tu modifies culpa, so we use the non-accented form.

In Spanish, subject pronouns are often omitted because the verb ending shows who the subject is.

• estás already tells us it’s tú (you, singular informal).
• So “si estás cansada” is completely natural and typical.

You can say “si tú estás cansada”, but:

• It usually adds emphasis or contrast, like:
  
  • Si tú estás cansada, imagínate yo.
    
    • If you are tired, imagine me.

In this neutral sentence, the version without the pronoun sounds more natural.

• si (no accent) = “if” (conditional).
  
  • si estás cansada = if you are tired.
• sí (with accent) = “yes” or “oneself” (in some reflexive uses).
  
  • Sí, estoy cansada. = Yes, I’m tired.

Here we’re expressing a condition (if you are tired), so we use si without an accent.

The semicolon in Spanish works similarly to English: it connects two related but complete sentences.

• No es tu culpa si estás cansada;
  Complete sentence (it has a subject, verb, and full idea).

• nadie es capaz de trabajar bien sin descanso.
  Another complete sentence.

A semicolon shows a close logical connection between the ideas (“it’s not your fault” ↔ “nobody can work well without rest”) without fully separating them like a period would.

You could use a period instead, but the semicolon nicely ties them together.

Ser capaz de + infinitive literally means “to be capable of doing something”.

• Nadie es capaz de trabajar bien sin descanso.
  = Nobody is capable of working well without rest.

Poder + infinitive means “to be able to / can”, often more practical or immediate ability:

• Nadie puede trabajar bien sin descanso.
  = Nobody can work well without rest.

In this context, both are possible, but:

• es capaz de sounds a bit more general/absolute: no human being has the capacity to.
• puede can feel slightly more about practical ability: no one can manage to.

The meaning is very close; the original just has a slightly more general, “human nature” tone.

The phrase is fixed: ser capaz de + infinitive.

• Correct: es capaz de trabajar (is capable of working)
• Incorrect: es capaz a trabajar, es capaz para trabajar (in this meaning)

So you can make many sentences like:

• Soy capaz de hacerlo. = I’m capable of doing it.
• No somos capaces de entender eso. = We aren’t capable of understanding that.

The preposition de is always used with capaz when followed by a verb.

Nadie means “nobody / no one” and it is grammatically singular in Spanish.

So we use third person singular verbs:

• Nadie es capaz… (not nadie son capaz).
• Nadie entiende. = Nobody understands.
• Nadie viene. = Nobody comes.

Even though it refers to an indefinite group of people, grammatically it behaves like “no one” in English, not like “people”.

Both are possible, but they differ slightly in nuance:

• sin descanso
  
  • Literally “without rest” (rest in general, as a concept).
  • Sounds more general/abstract: without rest at all.
• sin un descanso
  
  • Literally “without a break / without a rest” (a specific instance).
  • Focuses more on not taking a particular break.

In a general statement about human limits, sin descanso is more natural and idiomatic.

This particular sentence is neutral and works in all Spanish-speaking regions.

A couple of notes relevant to Latin America:

• The “tú” form (estás) is common everywhere; in some regions you’ll also hear vos estás (voseo), but that would require changing other forms too.
• The structure No es tu culpa… and nadie es capaz de… is standard and equally natural across Latin America and Spain.

So you can safely use this sentence anywhere in the Spanish-speaking world.