Theodor Haecker, Journal in the Night, #295:
When a man perceives that the person he is talking to simply cannot see the things about which he is talking, then he should stop talking.
Footnotes to Plato from the foothills of the Superstition Mountains
Theodor Haecker, Journal in the Night, #295:
When a man perceives that the person he is talking to simply cannot see the things about which he is talking, then he should stop talking.
Never judge a book by its movie!
(Not a MavPhil original, I am sorry to say. Source? Paging Dave Lull.)
Seize the day and squeeze it for all the juice it's worth. Repeat tomorrow. And no day without a little Emerson:
. . . we should not postpone and refer and wish, but do broad justice where we are, by whomsoever we deal with, accepting our actual companions and circumstances, however humble or odious, as the mystic officials to whom the universe has delegated its whole pleasure for us. (From "Experience")
Al-Ghazzali, The Alchemy of Happiness, p. 48:
Another dangerous property of worldly things is that they appear at first as mere trifles, but each of these so-called 'trifles' branches out into countless ramifications until they swallow up the whole of a man's time and energy.
Die Fehler sind alle schon da, sie warten nur darauf, gemacht zu werden. (Savielly Tartakower)
The mistakes are already all out there just waiting to be made. (tr. BV)
"Let me never fall into the vulgar mistake of dreaming that I am persecuted whenever I am contradicted."
Ralph Waldo Emerson, 8 November 1838
"The nearer we are to the mountain, the smaller we are. The nearer to eternal Sanctity, the more sinful we seem to ourselves to be." (Claudel-Gide Correspondence, p. 91)

Theodor Haecker, Journal in the Night (tr. Alexander Dru, Pantheon Books, 1950, p. 36, #146):
The truly philosophical spirit is a contemplative spirit. It is not captivated by the things that one can change, but but by those, precisely, which cannot be changed.
Theodor Haecker, Journal in the Night (Pantheon, 1950, tr. Dru), #689, p. 212, written in 1944:
The endless chatter about Nietzsche and Kierkegaard is quite hopeless. Outward similarities set up a superficial sphere of comparison that is utterly meaningless, for they are localised and limited by a decisive difference at a deeper level; the one prayed, the other did not.
I am petty; nothing petty is foreign to me. Or to my journal.
Richard Weaver, "Life Without Prejudice" in Life Without Prejudice and Other Essays, Chicago: Henry Regnery, 1965, p. 11:
Upon one occasion when Boswell confessed to Johnson that he feared some things he was entering in his journal were too small, the latter advised him that nothing is too small for so small a creature as man.
"The sky is the daily bread of the eyes," wrote Ralph Waldo Emerson magnificently and truly. And this from a man who lived in New England where there is no sky to speak of. What would he have written had he been able to bathe his thoughts in the lambent light of the desert Southwest?
I sing the praises of Joseph Joubert, but here is a very bad aphorism of his:
The style is the thought itself. (Notebooks, p. 44)
This is an exaggeration so absurd that not even a Frenchman should be allowed to get away with it. Much, much better is this brilliancy from the pen of Schopenhauer:
Style is the physiognomy of the mind.
Reader RP submits the following aphorisms for evaluation:
A very good thing about not having anyone to talk to is not having to talk to anyone.
A very good thing about not having any place to go to is not having to go anyplace.
The evil of loneliness becomes the good thing of solitude when one makes use of all the time on one's hands by thinking and loving God.
Do they meet your standard for aphorisms?
Brevity and economy of expression are marks of a good aphorism. Hackneyed phrases such as "time on one's hands" ought to be avoided. I would rewrite your first and third like this:
The good of not having anyone to talk to is not having to talk to anyone.
and
The alleviation of loneliness is not in society but in solitude with Him Who Is.
or
Amor dei transmutes the evil of loneliness into the good of solitude.
A good aphorism ought to be brief, true, original, satisfying in form, and universal in content. Example:
A man sits as many risks as he runs. (Thoreau)
That is a model aphorism. You say it is not true as it stands? But add some such qualification as 'in many cases' and you remove its literary merit. Besides, anyone intelligent enough to understand it will take the qualification as tacitly present. Even better, perhaps, is
Some men are born posthumously. (Nietzsche)
The proposition this expresses is true without qualification. Here is one from E. M. Cioran, Drawn and Quartered (New York: Seaver Books, 1983, translated from the French by Richard Howard):
Conversation is fruitful only between minds given to consolidating their perplexities. (163)
Brilliant. Philosophy, as Plato remarks (Theaetetus St. 155) and Aristotle repeats (Metaphysics 982b10), is about wonder, perplexity. Fruitful philosophical conversation, rare as it is and must be given the woeful state of humanity, is therefore a consolidation and appreciation of problems and aporiai, much more than an attempt to convince one’s interlocutor of something. Another from Cioran:
Nothing makes us modest, not even the sight of a corpse. (87)
Outstanding! But this is bad:
Time, accomplice of exterminators, disposes of morality. Who, today, bears a grudge against Nebuchadnezzar? (178)
This is quite bad, and not become of its literary form, but because the thought is false. If enough time passes, people forget about past injustices. True. But how does it follow that morality is abrogated? Cioran is confusing two distinct propositions. One is that the passage of time disposes of moral memories, memories of acts just and unjust. The other is that the passage of time disposes of morality itself, rightness and wrongness themselves, so that unjust acts eventually become neither just not unjust. The fact that Cioran’s aphorism conflates these two propositions is enough to condemn it, quite apart from the fact that the second proposition is arguably false. A good aphorism cannot merely be clever; it must also express an insight. An insight, of course, is an insight only if it is true. Nor is an aphorism good if it merely betrays a mental quirk of its author. For then it would be of merely psychological or biographical interest.
An aphorism is not a proverb such as
Aus den Augen, aus den Sinn
Out of sight, out of mind.
or
Neue Besen kehren gut
A new broom sweeps clean.
A proverb is a distillation of folk wisdom; an aphorism is the product of an individual.
An aphorism is not a maxim such as
Do unto others as you would have them do unto you.
Maxims are prescriptive; aphorisms descriptive. They are grammatically declarative rather than imperative or optative or cohortative.
Must an aphorism be a standalone? The following makes a good aphorism even though it is part of a wider context:
Life is a business that doesn't cover its costs. (Schopenhauer)
Finally, Karl Kraus on the art of the aphorism:
Beim Wort Genommen, p. 132:
Einen Aphorismus zu schreiben, wenn man es kann, ist oft schwer. Viel leichter ist es, einen Aphorismus zu schreiben, wenn mann es nicht kann.
It is often difficult to write an aphorism, even for those with the ability. It is much easier when one lacks the ability. (tr. BV)
A stunning formulation for your delectation from the translator of Plato and the don of Balliol College:
Grace is an energy; not a mere sentiment; not a mere thought of the Almighty; not even a word of the Almighty. It is as real an energy as the energy of electricity. It is a divine energy; it is the energy of the divine affection rolling in plenteousness toward the shores of human need.
An observation magisterial on all counts, combining as it does truth, economy of expression, and literary beauty: "the energy of the divine affection rolling in plenteousness toward the shores of human need." Could it do with a bit of paring? How about this:
. . . the energy of God's plenary affection rolling shoreward toward human need.
Companion posts: