The Public and the Private Domain

Reb Yisrael Salanter said "How you feel inside is a reshus hayachid.   Your face is a reshus harabbim."  Reb Yisrael was using the language of Bava Kamma, where we are told that one may dig holes or leave things lying around on his private property, where outsiders are not allowed to enter and the only person affected is himself.  But if one digs a hole or leaves a stumbling block in a public place, he is liable for any resulting damages and injuries.  How you feel inside is your private affair.  But your behavior and appearance affect the people around you, and you are obligated to present a happy appearance so as not to hurt the people that see you.

The Mesillas Yesharim in the seventh perek says:

ואמנם כבר ידעת, שהנרצה יותר בעבודת הבורא, יתברך שמו, הוא חפץ הלב ותשוקת הנשמה. והוא מה שדוד המלך מתהלל בחלקו הטוב ואומר (תהלים מב): כאיל תערג על אפיקי מים כן נפשי תערוג אליך אלקים, צמאה נפשי לאלקים וגו'. (שם פד): נכספה וגם כלתה נפשי לחצרות ה'. (שם סג): צמאה לך נפשי כמה לך בשרי. ואולם האדם אשר אין החמדה הזאת לוהטת בו כראוי, עצה טובה היא לו שיזדרז ברצונו, כדי שימשך מזה שתולד בו החמדה בטבע, כי התנועה החיצונה מעוררת הפנימית, ובודאי שיותר מסורה בידו היא החיצונה מהפנימית. אך אם ישתמש ממה שבידו, יקנה גם מה שאינו בידו בהמשך, כי תולד בו השמחה הפנימית והחפץ והחמדה מכח מה שהוא מתלהט בתנועתו ברצון. והוא מה שהיה הנביא אומר (הושע ו): ונדעה נרדפה לדעת את ה', וכתוב (שם יא): אחרי ה' ילכו כאריה ישאג.

For current purposes, one of the things he says here is that it is very hard to directly change how we feel, but our external behaviors do influence and can eventually modify our emotional state.  

The two reasons for acting cheerful despite how you really feel can be restated succinctly, albeit pedantically (1).  Our affect (2) affects (3) the people around us, so affectation (4) might be a civic duty.  Sometimes, affectation is the best way to effect (5) change in our own emotions.
1.  Pedantically:  Characterized by ostentatious display of formal scholarship.
2.  Affect (Noun): the observable manifestation of feelings.
3.  Affects (Transitive Verb): influences or causes change   
4.  Affectation (Noun): the display of feelings not genuinely felt
5.  Effect (Transitive Verb):  cause or bring about, especially used in overcoming resistance.

I once heard a drasha from Reb Sholom Shvadron on the pesukim in Malachi 3 

ואמרתם, במה נשוב.  היקבע אדם אלוקים כי אתם קובעים אותי ואמרתם במה קבענוך:  המעשר, והתרומה.  במארה אתם ניארים ואותי אתם קובעים הגוי כולו.... חזקו עליי דבריכם, אמר ה' ואמרתם מה נדברנו עליך.  אמרתם, שוא עבוד אלוקים ומה בצע כי שמרנו משמרתו וכי הלכנו קדורנית מפני ה' צבאות

Can a man blaspheme the Lord as you have? And you say, how have we blasphemed?.... You have used strong words against me, says Hashem.  You say, what did we say?  You said it is futile to serve the Lord, what benefit is there in observing his observances, we accomplish nothing in our lives because of Hashem.

Reb Sholom asked, if that's what they said, why did they claim innocence?  If they used such blasphemous, chutzpedikeh language, they would have fully aware of their disloyalty and their sin and, while talking to the Navi who could see the truth, admitted it.  They seem honestly bewildered, they sincerely have no idea of what they did wrong.  How could they have been totally oblivious of such a grievous sin?  He answered that they never chas veshalom actually said these things.  On the contrary, they were meticulous in their observance.  The problem was that they would walk around like the weight of the world was on their shoulders, as if being a frum Jew was a heavy burden and an unpleasant obligation.  By walking around with this look on their faces, they are essentially making a public proclamation that they dislike having to do the mitzvos and not do aveiros and they would be thrilled to free themselves from those obligations.  Nobody cares if an employee that you hire likes you or not.  But a servant is not just an employee.  A servant to his master is like a subject to his king.  He is a member of the master's household.  A servant that makes it clear that his duties are a burden he dreams of removing, that he wishes you weren't his master, is not a good servant, no matter how efficient and skilled he is.  He is a constant offense to his master.  The dour mien, the dragging feet, the "let's get it over with" davening, all of these loudly declare "I wish I didn't have to do this."

Rabbi Moshe Goldberger, of the Yeshiva of Staten Island, wrote the following:

A smile costs nothing, but gives much. It reaches those who receive without making poorer those who give. It takes but a moment, but the memory can sometimes last a lifetime.

None is so rich or mighty that he can get along without it and none is so poor but that he cannot be made richer by it.

A smile creates happiness in the home, fosters goodwill in business, and is the countersign of friendship. It brings rest to the weary, cheer to the discouraged. A smile is sunshine to the sad and is nature’s best antidote for trouble.

Yet it cannot be bought, begged, borrowed or stolen, for it is of no value to anyone until it is given away. Some people are too tired to give you a smile. Give them one of yours, as none needs a smile so much as he who has none to give.

I saw these ideas presented very well in a video by Dennis Prager, here.  (Dennis Prager went to Yeshiva of Flatbush and RJJ, and his brother is Orthodox, but he is no longer observant.   I assume he is aware of the two references above.   Mr. Prager is not only fluent in Russian, but he can also read Hebrew backwards as well as he can forwards, a skill he developed while trying to kill time at RJJ.)