'Success' is also the root word for 'succession' and the like, meaning to move forward one after the other. We tend to learn the word 'success' to mean 'accomplishment' but that is only part of it. You have to add the implied 'moving one after the other'.
Many folks have become 'successful' but can also stop being successful. So, being a success is a temporary state. If you stop accomplishing things (plural) then you stop being successful.
No I'm not an english major, but to stop boring everyone I'll just say my definition of success is to be better, know more, have more skill than I did the last go around. As long as all that is in an upward trend, then I am successful and happy about it.
GG