Seneca begins the letter with,
I shall now tell you certain things to which you should pay attention in order to live more safely.
That word 'safely' is interesting. If a Stoic is concerned about safety (physical and rational), I would balk at that. Safety is a bit of an external or indifferent. But then, I observe the title of the letter and perhaps Seneca means 'safely' in terms of living confidently - being secure in one's own philosophy; at least that is how I'm reading this.
Next he takes on the root causes of humanities problems; what motivates people to seek the destruction of others?
Reflect on the things which goad man into destroying man: you will find that they are hope, envy, hatred, fear, and contempt.
Hope and envy, somewhat, go hand in hand. Because one person lacks something (AND they think that they need it), envy stirs within them and they hope to get what others have.
How do you safely avoid these people?
you can avoid the envious hopes of the wicked so long as you have nothing which can stir the evil desires of others, and so long as you possess nothing remarkable. For people crave even little things, if these catch the attention or are of rare occurrence.
Seneca says one way to prevent envy is to simply not possess things which may cause it. This sounds like a resounding endorsement for minimalism.
Another way to avoid the envy of others is to simply keep quiet about your status and possessions.
You will escape envy if you do not force yourself upon the public view, if you do not boast your possessions, if you understand how to enjoy things privately.
As for avoiding the hatred of others, he writes,
Hatred comes either from running foul of others: and this can be avoided by never provoking anyone; or else it is uncalled for: and common-sense will keep you safe from it. Yet it has been dangerous to many; some people have been hated without having had an enemy.
Either never provoke someone, or perhaps choose a path of de-escalation.
You can prevent others' fears of you by being of
a moderate fortune and an easy disposition.
And then there is the matter of avoiding others' contempt for you. The best thing to do is to keep still and talk little of yourself with others.
Nothing, however, will help you so much as keeping still – talking very little with others, and as much as may be with yourself.
You could apply all these little tactics to be able to live safely and confidently. Alternatively, you could do one thing: do no wrong.
The most important contribution to peace of mind is never to do wrong. Those who lack self-control lead disturbed and tumultuous lives. ... A wrongdoer sometimes has the luck to escape notice but never the assurance thereof.