Southend chief executive Gary Lockett has resigned with immediate effect but will remain as a non-executive director.
Lockett only took the position with the League Two club on March 1 but he admits he has struggled to balance the demands of the job with his own business interests.
Lockett told Southend's official website: "The role is more demanding than I first appreciated and I have had to juggle my other responsibilities.
"The chairman, quite rightly, is very ambitious for the club's success, as I am. And although Ron (Martin) originally described the role as 24/7 I perhaps did not appreciate that that is precisely what is required, and to balance my other business interests and meet the club's needs also is simply not practical.
"Nevertheless the chairman has invited me to remain as a non-executive director which I am very happy to do and look forward to helping him and the rest of the board advance the club, including its move to the new stadium."
Lockett took over from Tara Brady following his resignation earlier this year and Southend have now started their search for a third chief exec in the space of eight months.