G. Reale, A History of Ancient Philosophy: The Schools of the Imperial Age, trans. John R. Catan (Albany: State University of New York Press, 1990) 465-466.
[Seneca] returned to Rome and participated actively and successfully in the political life. In 41 CE Seneca, because of the shady maneuvers of Messilina was sent into exile in Corsica. Only in 49 CE could he return to Rome, when after the elimination of Messilina, Aggripina recalled him to supervise the education of her son Nero.
In 54 Nero became Emperor, from then on for many years Seneca, together with Burrus (prefect of the praetorium) had great political influence and responsibility, but without taking on any official public office, simply in their role as counselors to the Emperor. In 62 CE Burrus died, Seneca, retired from public life, being by this time out of favor with Nero, as well as because of the malificent influence of Poppea. This however did not allay the suspicions of Nero, who discovered, in 65 CE, the plot organized against him by Calpurnius Piso. Seneca was accused of secret dealings with Piso and he was condemned to suicide. Seneca took his own life with Stoic fortitude and great equanimity of soul. The works of Seneca are very rich...
As you can see, Seneca had a lot of highs and lows, ups and downs. Right when he reaches a position of influence, he is suddenly demoted, only to rise and then fall again. He is betrayed by those he helps, showing that the favor of people is not necessarily iron-clad.
Yet, through all of this, he writes things that touch and influence many people, as he maintains "fortitude and great equanimity" in his soul. He reminds me of the apostle Paul, who was a contemporary of his. Paul had his ups and downs. Some towns accepted him and his message, while others stoned him. Some of the churches he founded appreciated his work on their behalf; others did not. Sometimes, Paul felt refreshed by the company of his brothers and sisters in Christ (Acts 28:15); sometimes, his felt abandoned by them (II Timothy 4:16-17).
Paul did not exactly arrive at his inner peace the same way that Seneca did. Seneca tried to suppress his emotions, whereas Paul trusted God's love for him and had the hope of a good afterlife. Both, however, left a positive mark on this world: Seneca influenced government, and Paul exposed people to the love of God in Jesus Christ his Lord. Regardless of their ups and downs, they had a purpose in life, and they clung to it with tenacity.