Después del trabajo, estoy cansadísimo y me acuesto temprano.

Because de + el contracts to del in Spanish.

So:

• de el trabajo → del trabajo

This contraction is mandatory when el is the masculine singular definite article.

A similar common contraction is:

• a + el → al

Note: this only happens with the article el, not with the pronoun él.

In Spanish, trabajo here refers to work as a specific thing in your daily routine, so the definite article el is natural.

• después del trabajo = after work / after the workday

Spanish often uses articles where English does not. So even though English says after work, Spanish normally says después del trabajo.

You could also hear:

• después de trabajar = after working

But después del trabajo is the most direct match for after work in this sentence.

Because estar is used for states or conditions, and being tired is a temporary condition.

• estoy cansado = I am tired
• soy cansado would not mean the same thing and would sound wrong here

A useful rule:

• ser = identity, characteristic, origin, etc.
• estar = condition, state, location, result

Since tiredness is a state that can change, Spanish uses estar.

Cansadísimo means extremely tired, very, very tired, or absolutely exhausted.

It comes from:

• cansado = tired
• -ísimo = a suffix that intensifies the adjective

So:

• cansado = tired
• cansadísimo = very/extremely tired

This ending is very common in Spanish:

• grande → grandísimo
• bueno → buenísimo
• guapo → guapísimo

It is stronger and more expressive than just saying muy cansado.

It agrees with the person being described.

Here, the speaker is grammatically masculine singular:

• cansadísimo = masculine singular

If the speaker were female, it would be:

• cansadísima

If talking about more than one person:

• cansadísimos = masculine or mixed plural
• cansadísimas = feminine plural

So the ending changes just like a normal adjective.

Because the verb is acostarse, which is a reflexive verb.

• acostarse = to go to bed / to lie down

The me matches I:

• me acuesto = I go to bed
• te acuestas = you go to bed
• se acuesta = he/she goes to bed

In English, we do not usually say I put myself to bed in this context, but Spanish uses the reflexive form naturally.

So me acuesto temprano means I go to bed early.

Because acostarse is a stem-changing verb in the present tense.

The o in the stem changes to ue in most forms:

• me acuesto
• te acuestas
• se acuesta
• nos acostamos
• os acostáis
• se acuestan

So yo acuesto is the correct present-tense form, not yo acosto.

This kind of change is very common in Spanish. Similar verbs include:

• dormir → duermo
• volver → vuelvo
• contar → cuento

It can mean either, depending on context.

In this sentence, the natural meaning is:

• I go to bed early

That is because the rest of the sentence talks about being very tired after work, so bedtime makes the most sense.

In another context, acostarse could also mean to lie down.

Because Spanish often leaves out subject pronouns when the verb already makes the subject clear.

• estoy already means I am
• me acuesto already means I go to bed

So yo is unnecessary unless you want emphasis or contrast.

For example:

• Yo estoy cansadísimo, pero él no. = I’m extremely tired, but he isn’t.

Without special emphasis, Spanish usually omits yo.

Here temprano is being used as an adverb, meaning early.

• me acuesto temprano = I go to bed early

When used as an adverb, it does not change for gender or number.

Compare:

• una hora temprana = an early hour
  Here temprana is an adjective, so it agrees with hora.
• llego temprano = I arrive early
  Here temprano is an adverb, so it stays the same.

Y simply means and. It joins the two parts of the sentence:

• estoy cansadísimo = I’m extremely tired
• me acuesto temprano = I go to bed early

So the full sentence presents two connected ideas:

• after work, I’m extremely tired
• and I go to bed early

It is the normal Spanish word for and.

The phrase Después del trabajo is an introductory time expression, and the comma helps separate it from the main clause.

• Después del trabajo, estoy cansadísimo y me acuesto temprano.

In informal writing, some people might omit the comma, and the sentence would still be understandable. But using the comma is very natural and helps readability.

It works like English:

• After work, I’m extremely tired and I go to bed early.