Avot143

8:
When we speak of God's unity what do we really mean? Rambam teaches that true belief in God's unity inevitably implies belief in a non-physical Deity – a Deity that does not exist as part of the physical universe, a Deity that "is not physical and has no physical appearance" [this is part of a line from the hymn Yigdal, which itself is a verse rendition of Rambam's Thirteen Principles first enunciated in his Mishnah Commentary]. One who conceives of God (other than metaphorically, of course) as being an old man or king with a long white beard, white robes, seated upon a high and lofty throne somewhere in the farthest reaches of heaven, surrounded by angels who play unceasingly on harps – one who believes in such a God is an idolater pure and simple! Such a person does not believe in the God of Israel.

9:
The One God exists, but because God is not a part of the physical universe, God's existence can only be comprehended intellectually and emotionally in the mind and heart of the believing Jew. It is this conceptualization of the divine essence that the Jew affirms when declaring, twice daily, Shema Yisra'el Adonai Eloheynu Adonai Eĥad: God is, God is God, and God is unitary.

10:
It is but fitting that this supreme declaration of belief be recited with appropriate concentration. A conscious effort should be made to think about what the words mean; this is all the more difficult when we recall that the Shema is recited so often that it becomes almost second nature to do so – and if it is sung the problem is further compounded. Thus a determined effort of concentration is required. The first parashah of the Shema contains truths and customs that are basic to Judaism, which is why it is singled out for especial concentration: belief in God's unity, love of God, Jewish education, recitation of the Shema every morning and every evening, Tefillin, Mezuzzah – we cannot imagine Judaism without these, and they are all there in that first short passage. And the second parashah, dealing as it does, with the doctrine of reward and punishment is an essential concomitant to acceptance of the duty to observe the mitzvot. And the third parashah of the Shema introduces the mitzvah of Tzitzit, which are intended to be a constant reminder of God's requirements of us. All these considerations are sufficient to understand why Rabbi Shim'on ben-Netan'el sees a special need to recite the Shema very carefully.

Personal experience has taught Meir Stone that the warning is by no means trite:

Nearly every job I have ever worked I have always heard someone say, "It is not my money so why not be wasteful?".

I respond:

As Marcus Tullius Cicero said: O tempora, O mores! And as Rabbi Yehoshu'a said: Oy la-dor [woe to such a generation].

Gregory Ashe writes:

In response to the Tur's suggestion of living a life totally devoted to the service of God you responded [Avot 141]:

It seems to me that anyone who claims to live his life according to these precepts is either a superhuman saint or is a fool full of self-deception. Surely, in such matters it is the striving which is important even if very few indeed will reach achievement, if at all.

Perhaps that is what is so powerful about the concept of the beinoni [average man – SR] developed in the Tanya (at least as much as I can understand it through Rabbi Steinsaltz's book "Opening the Tanya"): the Tanya recognizes that we are not superhuman, but that life is a constant struggle as we muddle through the middle. What is important is that we are struggling in the right direction, not that we always "get it right."

I respond:

This is true. But I think that it is helpful from time to time to recall that most people cannot maintain very high standards of piety for an indefinite period. When the young scholar Israel-Meir Kagan presented his work Shemirat ha-Lashon (Ĥafetz Ĥayyim) on the laws of Lashon ha-Ra [wicked speech] to the great Rabbi Israel Salant (the founder of the Musar Movement) for approbation the latter responded: "Reb Israel-Meir, every Jew should read your book – even if the only result will be that he heave a great sigh!"