Expressing consequences (por eso)

When things don't go according to plan, connect a cause to its logical consequence using por eso ("that's why" or "therefore").

therefore / that's why
por eso

State the reason first, add a comma, then introduce the result with por eso:

The alarm clock isn't ringing, that's why I keep sleeping.
El despertador no suena, por eso sigo durmiendo.
The connection is failing, that's why I am leaving the meeting.
La conexión está fallando, por eso salgo de la reunión.

Excuses and Apologies

Por eso is perfect for giving excuses or explaining why you are late. State the problem, followed by por eso and your action or apology.

I have an urgent problem, that's why I cannot attend.
Tengo un problema urgente, por eso no puedo asistir.
The train has a delay, that's why I notify you.
El tren tiene un retraso, por eso te aviso.
It is my fault, that's why I apologize to you.
Es mi culpa, por eso me disculpo contigo.

Blame and Fault

Use the noun la culpa (fault/blame) to assign responsibility or admit a mistake.

fault / blame
la culpa
You are to blame for this error, that's why you must correct it.
Tú tienes la culpa de este error, por eso debes corregirlo.