This question regards Matthew 5:20:

"For I say to you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, you shall in no case enter into the kingdom of heaven."

and the orthodox interpretation of it. I found this site that basically says that the fasting on Monday is done by monks, but also observed by pious orthodox believer that ye may exceed the righteousness of scribes and Pharisees.

Is that why orthodox fast on Monday?

I don't mean to be rude, but I find much of orthodox theology concerning Theosis to be pelagian, as trying to earn heaven by merit, and while I know that the Orthodox Church does not teach that one can enter heaven by it's own power. It still feels like some strive from the bottom of their being to be more pious and righteousness that others, as it were a race, where Christ stands passive and the end of the ladder, while sinners try desperately to climb the ladder, always climbing never reaching the end. Always admiring the saints, never daring to feel worthy. And even know never daring to feel worthy, still, always fearing and questing, am I good enough, will I be received.

Being told that the saints themselves where not sure if they are saved, then, much more shall the laity fear their fate.