What's the use, after all, of mastering a horse and controlling him with the reins at full gallop if you're carried away yourself by totally unbridled emotions? - Seneca
What is really great about Stoic (and particularly Seneca's) advice on life is that they are not extreme - rather, they call for balance and modesty. Jonathan Haidt points this out in The Happiness Hypothesis:
Neither Buddha nor the Stoics urged people to withdraw into a cave. In fact, both doctrines have such enduring appeal precisely because they offer guidance on how to find peace and happiness while participating in a treacherous and ever-changing social world.
Consider the following advice - the first one on how to become a better man and the second on the difference between a wealthy and a poor man:
...refrain from following the example of those whose craving is for attention, not their own improvement, by doing certain things which are calculated to give rise to comment on your appearance or way of living generally...Let our aim be a way of life not diametrically opposed to, but better than that of the mob.
It is not the man who has too little who is poor, but the one who hankers after more... You ask what is the proper limit to a person's wealth? First, having what is essential, and second, having what is enough.
The Criticisim of Education
The letter that left the strongest impression on me is the Letter LXXXVIII, where Seneca discusses the liberal studies (and essentially this can be applied to the entire education of today):
You want to know my attitude towards liberal studies. Well, I have no respect for any study whatsoever if its end is the making of money. Such studies are to me unworthy ones. They involve the putting out of skills to hire, and are only of value in so far as they may develop the mind without occupying it for long. Time should be spent on them only so long as one's mental abilities are not up to dealing with higher things. They are our apprenticeship, not our real work. Why 'liberal studies ' are so called is obvious: it is because they are the ones considered worthy of a free man.* But there is really only one liberal study that deserves the name - because it makes a person free - and that is the pursuit of wisdom.
The question has sometimes been posed whether these liberal studies make a man a better person. But in fact they do not aspire to any knowledge of how to do this, let alone claim to do it. Literary scholarship concerns itself with research into language, or history if a rather broader field is preferred, or, extending its range to the very limit, . poetry. Which of these paves the way to virtue? Attentiveness to words, analysis of syllables, accounts of myths, laying down the principles of prosody? What is there in all this that dispels fear, roots out desire or reins in passion? Or let us take a look at music, at geometry; you will not find anything in them which tells us not to be afraid of this or desire that - and if anyone lacks this kind of knowledge all his other knowledge is valueless to him.
Teach me instead what purity is, how much value there is in it, whether it lies in the body or in the mind. Turning to the musical scholar I say this. You teach me how bass and treble harmonize, or how strings producing different notes can give rise to concord. I would rather you brought about some harmony in my mind and got my thoughts into tune. You show me which are the plaintive keys. I would rather you showed me bow to avoid uttering plaintive notes when things go against me in life.
You geometers can calculate the areas of circles, can reduce any given shape to a square, can state the distances separating stars. Nothing's outside your scope when it comes to measurement. Well, if you're such an expert, measure a man's soul; 'tell me how large or how small that is. You can define a straight line; what use is that to you if you've no idea what straightness means in life?
"I look for the best and I am prepared for the opposite"
Further on in Letter LXXXVIII, Seneca prepares us to cope with randomness of everyday life. Things will happen in the world wheter or not you understand them; but what is important is that you stay prepared and know how to deal with them. (Also, regarding this, a great modern complement to Seneca is Nassim Taleb's book Antifragile: Things That Gain From Disorder).
What is to be gained from this sort of knowledge? Am I supposed to feel anxious when Saturn and Mars are in opposition or Mercury sets in the evening in full view of Saturn, instead of coming to learn that bodies like these are equally propitious wherever they are, and incapable of change in any case. They are swept on in a path from which they cannot escape, their motion governed by an uninterrupted sequence of destined events, making their reappearances in cycles that are fixed. They either actuate or signalize all that comes about in the universe. If every event is brought about by them, how is mere familiarity with a process which is Wlchangeable going to be of any help? If they are pointers to events, what difference does it make to be aware in advance of things you cannot escape? They are going to happen whether you know about them or not.
I've taken sufficient precautions, more than sufficient precautions, to ensure that I'm not taken in by deceptive phenomena. At this you'll protest: 'Can you really say "the day that follows never proves me wrong"? Surely anything that happens which one didn't know in advance was going to happen proves one wrong?' Well, I don't know what's going to happen; but I do know what's capable of happening - and none of this will give rise to any protest on my part. I'm ready for everything. If I'm let off in any way, I'm pleased. The day in question proves me wrong in a sense if it treats me leniently, but even so not really wrong, for just as I know that anything is capable of happening so also do I know that it's not bound to happen. So I look for the best and I am prepared for the opposite.