إذا قمت في صلواتك فصل صلاة مودع 

 ولا تتكلم بكلام تعتذر منه

 واجمع الإياس مما في أيدي الناس

An individual approached Prophet Muhammad (Allah bless him and give him peace) and requested for some concise advice.

The Prophet (Allah bless him and give him peace) said,

At the time of offering salat, pray as if this is your last prayer.

And

Do not speak anything for which you will have to apologize later.

And

Do not have any desire for what other people possess.

Ahamd via Jawahar al-Hikam, page 23