There was a Final Sermon that the Prophet Muhammad (SAW) gave to the people.

We were told in this, amongst other things, that:

"Beware of Satan, for the safety of your religion. He has lost all hope that he will ever be able to lead you astray in big things, so beware of following him in small things."

So - he may not be able to stab you in the heart (convince you that Allah doesn't exist) but he will tie your shoe laces so fall flat on your face in the mud (get you to focus / concentrate on the smaller things so much that you place less importance on the bigger things)