Essex knew they needed something different in the second-half and came out raring to go with their first big chance coming soon after. Jess Norey found himself in acres of space with just Taylor Seymour to beat but his strike drifted agonisingly wide.
Sussex responded, however, thanks once again to a super stop by Allan, Demas Ramsis was denied from close range.
Lovett decided fresh legs were needed at this point and subbed on Sam Wright and Reggie Ward looking for some more pace through the middle.
However, it just didn’t look like it was going to be Sussex’s day when, after striking against the post, Allan made a super save to stop Adam Bateman from tapping in.
Sussex, nevertheless, continued to push Essex back and finally found their opening when Santos’ effort that looked to be drifting wide was parried by Allan into the path of Wright who was on hand to strike home in to the far corner.
Essex looked to inject more firepower into their side by bringing on Sultan Sarni, and he started to pose more of a physical threat on the Sussex backline. Sarni almost had an immediate impact with room on the edge of the box to strike but Seymour saved smartly to maintain the lead.
Sussex responded themselves looking for the all-important second goal but Allan was to ensure that wouldn’t be the case, well-saving a fearsome volley from Fin Stevens. From the resulting corner, another opportunity went begging with as Popham headed inches wide of the near post.
Then, Sussex looked like they were going to be made to pay for those missed chances when Seymore brought down Rashaad Ogun, and the referee duly pointed to the spot. Sarni stepped up, however, Seymore redeemed himself making a fine save with his leg to ensure Sussex secured all three points.
Following the victory Sussex manager Jay Lovett said: "I thought it was going to be 1-1 but Taylor has pulled off a great save to keep us in the game. I'm very pleased with the way that we built up play from the back into the midfield who were also very creative in feeding the front line.
"We did everything right in and around the box all we didn't do was be clinical enough and put that ball in the back of the net as many times as we should have done.
"We did play very well but their 'keeper has also pulled off some great saves but on another day I think we would have won more comfortably.
"The style of football we played, as a neutral, I think you'll be very pleased to see in my opinion. To keep the shape the way we did and stick to that style was very very pleasing."