The short answer is, it's a mixed bag.
Sara and I have been reading Seneca's Epistles (ok, I've been reading aloud, while Sara knits!). We recently gave that up, after working through the first 27 letters in a Loeb edition. The idea was to learn our Latin together fast enough that we could read the Latin side of the page, too. But, the best laid plans, as they say...
Why did we give it up? For my part, it came down to "empty philosophy." There is much good here. I like especially the view of contenting ourselves with our lot, as the road to happiness. Just expect less, and you'll be happy. The simple life, etc. But then, Seneca will couch it in language like resigning oneself to one's fate. Hmmm, not quite right.
Or letter 28, on travel as a cure for discontent. To those who take this road (pun intended), Seneca wisely replies: "your faults will follow you whithersoever you travel.... The person you are matters more than the place to which you go." Pretty good stuff.
And then at the end of each letter he'll quote Epicurus - an interesting practice, since he represented an opposing school of thought, generally.
So I found this whopper at the end of letter 28 from Epicurus: "The knowledge of sin is the beginning of salvation." Seneca goes on: "He who does not know that he has sinned does not desire correction; you must discover yourself in the wrong before you can reform yourself."
Aaaagghh!! It was going along so well until those last 2 words! If only Seneca's brother, Gallio, would have given Paul a chance to speak (Acts 18:12ff), and let Seneca know about it.
Seneca's desire for righteousness and virtue is noble, yet he is wholly self-reliant to get there. Empty and vain men! If only Seneca's quote above had ended with "flee to Christ," instead of "reform yourself." But thank God, He has revealed this to us already.
Romans 3:20-22: "By the deeds of the law no flesh will be justified in His sight, for by the law is the knowledge of sin. But now the righteousness of God apart from the law is revealed, being witnessed by the Law and the Prophets, even the righteousness of God, through faith in Jesus Christ."