Como sigas tan agotado, mañana te costará mucho concentrarte en clase.

In this structure, como + subjunctive can mean if or if you keep..., often with a strong warning tone.

So:

• Como sigas tan agotado... = If you carry on being so exhausted...
• It often sounds more forceful than a neutral si sentence.

Here, como is not being used as how or like. It is part of a fixed conditional pattern:

• Como llegues tarde, nos vamos sin ti.
  = If you arrive late, we’re leaving without you.

This is very common in spoken Spanish when someone is warning, threatening, or stressing a consequence.

Because after como in this warning-style conditional, Spanish normally uses the present subjunctive.

So:

• Como sigas tan agotado... is correct.
• Como sigues... does not work in this meaning.

The verb sigas comes from seguir.

Present subjunctive of seguir:

• yo siga
• tú sigas
• él/ella siga
• nosotros sigamos
• vosotros sigáis
• ellos sigan

This use of the subjunctive helps signal that the situation is being presented as a possibility with a consequence, not simply stated as a fact.

Yes, you could say:

• Si sigues tan agotado, mañana te costará mucho concentrarte en clase.

This is perfectly natural and means basically the same thing.

The difference is tone:

• Si sigues... = more neutral, straightforward
• Como sigas... = more emphatic, more like a warning

So como here adds a sense of watch out — this will happen.

Agotado means exhausted, worn out, or drained.

Tan means so, and it is used before adjectives and adverbs to express degree:

• tan cansado = so tired
• tan lejos = so far
• tan agotado = so exhausted

So tan agotado means so exhausted.

A useful comparison:

• muy agotado = very exhausted
• tan agotado = so exhausted

In sentences with a consequence, Spanish often prefers tan:

• Está tan cansado que no puede estudiar.
  = He’s so tired that he can’t study.

It depends on who you refers to.

Spanish adjectives agree with the person they describe:

• agotado = masculine singular
• agotada = feminine singular

So:

• speaking to a man: Como sigas tan agotado...
• speaking to a woman: Como sigas tan agotada...

If you are talking to a group, it would change too:

• agotados
• agotadas

Literally, it means something like:

• it will cost you a lot

But in this context, costar often means:

• to be difficult
• to take effort
• to be hard for someone

So:

• te costará mucho concentrarte
  = it will be very hard for you to concentrate

This structure is very common:

• Me cuesta madrugar. = It’s hard for me to get up early.
• Nos costó entenderlo. = It was hard for us to understand it.
• Te costará mucho estudiar así. = It’ll be very hard for you to study like that.

The te shows for you.

In this kind of sentence, Spanish uses an indirect object pronoun with costar:

• me cuesta = it’s hard for me
• te cuesta = it’s hard for you
• le cuesta = it’s hard for him/her
• nos cuesta = it’s hard for us

So:

• mañana te costará mucho concentrarte
  = tomorrow it will be very hard for you to concentrate

Even though English often says you will find it hard, Spanish prefers this costar + indirect object + infinitive structure.

Because the sentence is talking about a consequence in the future:

• Como sigas tan agotado, mañana te costará mucho...
• If you keep being so exhausted, tomorrow it will be hard for you...

Since mañana clearly refers to tomorrow, the future tense costará fits naturally.

Spanish could sometimes use the present to talk about the future in conversation, but here the future tense sounds very normal and clear.

Because the verb is concentrarse, which is often used reflexively to mean to concentrate.

So:

• concentrarse = to concentrate
• concentrarte = for you to concentrate / to concentrate yourself

In practice, English just says to concentrate, but Spanish commonly uses the reflexive form.

Examples:

• No puedo concentrarme. = I can’t concentrate.
• Te costará concentrarte. = It will be hard for you to concentrate.

The te attached to the infinitive matches you.

They belong to two different parts of the sentence.

1. te costará
   Here, te means for you with the verb costar.

2. concentrarte
   Here, te is the reflexive pronoun belonging to concentrarse.

So the sentence contains:

• one te because something is hard for you
• another te because concentrarse is reflexive

That is completely normal in Spanish.

Here en clase most naturally means in class / during class.

It usually refers to the lesson situation, not just the physical room.

So:

• concentrarte en clase = to concentrate in class / during class

If you wanted to emphasise the physical classroom, Spanish might use something like:

• en el aula

But en clase is the normal everyday expression.

Yes, very much so.

This structure often sounds like:

• a warning
• a reproach
• a prediction of consequences

So the speaker is not just neutrally describing a possibility. They are saying something like:

• If you carry on like this, this is what’s going to happen.

That is why como + subjunctive often feels stronger than si.

It is:

• Como + present subjunctive, future consequence

So here:

• Como sigas tan agotado = conditional clause
• mañana te costará mucho concentrarte en clase = main clause with the consequence

A useful pattern to remember is:

• Como + subjunctive, + consequence
• Como no estudies, suspenderás.
• Como lleguéis tarde, no entráis.
• Como siga lloviendo, cancelarán el partido.

It is a very useful pattern for warnings in Spanish.