Once you're saved can you lose your salvation?

can a saved person lose their salvation through blasphemy? I'm afraid that maybe I did. I thought thought that blasphemy was to reject Jesus? Cause I did it out of ignorance but once I understood it I accpeted him and read the gospel of John and understood it. Liked it alot. It says in Ephesians that once you have heard the truth of the Gospel which I read it you are marked with a seal of The Holy Spirit. I also thought the one sin will send you to hell is dying without Jesus as your saviour, not two different sins