I think this is dealing with the idea of excess, as with intoxication by alcohol
You may be thinking that because you are thinking correctly about things you knew before you ever saw them in Seneca.
What Seneca is doing is dangerous however in repurposing Epicurean words for his own uses. Donald Robertson summarizes the issue well in this sentence:
"Indeed, Seneca is implicitly criticising Epicurus by pointing out that what is good in Epicureanism is not unique, and what is unique in it is not good."
And he has useful examples of this in his article here:
For example all of the following is from that article:
QuoteHe [Seneca] says several times that the quotes he draws from Epicurus typically articulate very commonplace ideas found in the writings of many earlier philosophers, poets, and playwrights. There are many ideas expressed by the Stoic school which we should not be surprised to find echoed elsewhere. However, that does not mean that the Stoics or Seneca agree with everything, or even the main things, said by these other authors. Indeed, Seneca is implicitly criticising Epicurus by pointing out that what is good in Epicureanism is not unique, and what is unique in it is not good.
By the ninth letter, Seneca is openly criticising Epicureanism, however. He rejects the Epicurean doctrine that the wise man needs friends to achieve the goal of living a truly pleasant life, free from fear and pain. The Stoic position is that the wise man is self-sufficient but that he prefers to have friends, fate permitting. Seneca quotes a letter of Epicurus as saying that the wise man needs friends for the reason:
QuoteThat there may be someone to sit by him when he is ill, to help him when he is in prison or in want.
Seneca, like other Stoics, criticises Epicurus for teaching his followers to develop what we call today “fairweather friendships”. Friends are valued by the Epicureans only as a means to the end of protecting their own peace of mind, comfort, and tranquillity. This is something Seneca, like other Stoics, sees as morally reprehensible. Seneca writes:
QuoteHe who regards himself only [i.e., his own self-interest], and enters upon friendships for this reason, reckons wrongly. The end will be like the beginning: he has made friends with one who might assist him out of bondage; at the first rattle of the chains such a friend will desert him. These are the so-called “fair-weather” friendships; one who is chosen for the sake of utility will be satisfactory only so long as he is useful. […] He who begins to be your friend because it pays will also cease because it pays. (Letter,
QuoteApparently in reference to the motto above the door to the Garden (“Stranger, here you will do well to tarry; here our highest good is pleasure.”) Seneca writes:
Choose, then, some honorable superscription for your school, some writing which shall in itself arouse the mind: that which at present stands over your door has been invented by the vices.