Eu sempre me esqueço de desligar a luz.

Because this sentence uses the verb esquecer-se de, which is a very common way to say to forget in Portuguese.

So:

• esquecer-se de algo = to forget something
• esquecer-se de fazer algo = to forget to do something

In Eu sempre me esqueço, me matches eu and means the verb is being used in its pronominal form.

Examples:

• Eu me esqueço
• Você se esquece
• Ela se esquece
• Nós nos esquecemos

In everyday Brazilian Portuguese, people also very often say Eu sempre esqueço de desligar a luz without me. That is extremely common in speech.

Esqueço is the first-person singular form of the verb esquecer(-se) in the present tense.

So:

• eu esqueço / eu me esqueço = I forget
• você esquece / você se esquece = you forget
• ele esquece / ele se esquece = he forgets

The ending -o is typical for many eu forms in the present tense.

Compare:

• eu falo = I speak
• eu como = I eat
• eu preciso = I need
• eu esqueço = I forget

So Eu sempre me esqueço literally means I always forget.

Because esquecer-se normally takes the preposition de before a noun or an infinitive.

Pattern:

• esquecer-se de + noun
• esquecer-se de + infinitive

Examples:

• Eu me esqueci do livro. = I forgot the book.
• Ela se esqueceu da reunião. = She forgot the meeting.
• Nós nos esquecemos de ligar. = We forgot to call.

So:

• me esqueço de desligar a luz = I forget to turn off the light

In informal Brazilian speech, you may also hear esquecer de without the pronoun:

• Eu sempre esqueço de desligar a luz.

Yes. In Portuguese, subject pronouns are often omitted because the verb ending already shows who the subject is.

So both are natural:

• Eu sempre me esqueço de desligar a luz.
• Sempre me esqueço de desligar a luz.

The second version is very common and sounds natural in Brazilian Portuguese.

People keep eu when they want to:

• emphasize the subject
• create contrast
• make the sentence clearer

For example:

• Eu sempre me esqueço, mas ela nunca esquece.

Sempre means always, and it usually goes before the main verb or after the subject.

In this sentence:

• Eu sempre me esqueço de desligar a luz.

That is a very natural placement.

You may also hear:

• Sempre me esqueço de desligar a luz.

Both are common.

Less natural for a learner, though sometimes possible depending on emphasis:

• Eu me esqueço sempre de desligar a luz.

So the safest choices are:

• Eu sempre me esqueço...
• Sempre me esqueço...

Portuguese often uses the definite article where English might not.

So:

• desligar a luz = turn off the light

This usually refers to a specific light in the situation, like the light in the room you are in.

Very similar expressions:

• abrir a porta = open the door
• fechar a janela = close the window
• lavar as mãos = wash your hands

In Portuguese, using the article here sounds natural and expected.

It is understandable and correct, but many Brazilians more often say apagar a luz.

So these are both possible:

• Eu sempre me esqueço de desligar a luz.
• Eu sempre me esqueço de apagar a luz.

Difference in feel:

• apagar a luz = the most common everyday expression for turning off a light
• desligar a luz = also possible, with a more general switch off idea

For electronic devices, desligar is especially common:

• desligar a TV
• desligar o computador
• desligar o ar-condicionado

For lights, apagar is often the most idiomatic choice.

In Brazilian Portuguese, both forms exist, and in real life people often use esquecer without the pronoun.

You will commonly hear:

• Eu esqueci o celular. = I forgot my phone.
• Eu esqueci de ligar. = I forgot to call.

And also:

• Eu me esqueci do celular.
• Eu me esqueci de ligar.

General idea:

• esquecer = very common, especially in conversation
• esquecer-se de = also common, and often seen as a more complete or more traditionally grammatical form

For a learner, it is useful to recognize both.

In this sentence, me esqueço de is perfectly good Portuguese.

The ç is there to keep the s sound.

The infinitive is esquecer. If Portuguese wrote the eu form as esqueco, the c before o would sound like k. That would be wrong.

So Portuguese changes it to ç:

• esqueço

This keeps the pronunciation like an s sound.

You see the same thing in other verbs:

• começar → eu começo
• conhecer → eu conheço

So the ç is a spelling change that protects the pronunciation.

It is in the present tense.

• Eu sempre me esqueço = I always forget

Even though English sometimes uses I’m always forgetting, Portuguese normally uses the simple present here.

This tense is often used for:

• habits
• repeated actions
• general truths

Since sempre shows a repeated habit, the present tense is exactly what you would expect.

Yes. That is a very natural English way to express the same idea.

The Portuguese sentence literally corresponds to:

• I always forget to turn off the light

But depending on context, natural English translations could be:

• I always forget to turn off the light.
• I keep forgetting to turn off the light.

So the Portuguese is talking about a repeated habit or recurring problem.

In careful pronunciation, yes, they are separate words:

• me = roughly mee
• esqueço = roughly es-KE-so or is-KE-so, depending on accent and speed

In normal fast Brazilian speech, me esqueço can sound more connected, almost like one rhythm group:

• meesqueço

But it is still two words:

• me
• esqueço

A rough pronunciation of the full sentence is:

• eh-ooh SEM-pree mee es-KE-soo djee dez-lee-GAR ah looz

That is only an approximation, but it can help you get started.