Boss John Maggs blamed a mad ten minutes as Horsham went down 3-2 at Dartford in their premier division opener.
Hornets led at the break through Russell Eldridge’s free-kick but Mark Knee gave away possession allowing Elliott Bradbrook to equalise.
Bradbrook then converted a penalty following a foul by Tony Achempong.
Adam Flanagan made it 3-1 before Pat Harding finished off a move down the left involving Eldridge and Alex Haddow to get his first Horsham goal.
Maggs said: “The better side lost and the performance wasn’t bad but we gave away two cheap goals in a mad ten minutes and it has cost us.”
Bognor did not enjoy a happy return to the league as they went down 3-0 at home to ten-man Hendon.
The Rocks lost their way after Jamie Busy was sent-off for the visitors in the 30th minute after a tussle with James Crane.
Mickey Demetriou had a golden chance to give Bognor the lead midway through the second half but Hendon went straight down the other end to score through James Bent.
Wayne O’Sullivan and Harry Hunt caught Bognor out twice on the counter attack in the final ten minutes.
Rocks boss Darin Killpartrick said: “The game changed when they had a player sent-off. Having an extra man didn’t help us as they sat back and hit us on the break.
“What upset me most was that we gifted them three goals and failed to take a handful of chances ourselves.”
Liam Upton hit a post and Scott Ramsay and Lee Carey failed to take good opportunities as Hastings United were held to a 0-0 draw at Boreham Wood.
Boss Tony Dolby said: “We had the better chances. It was a promising performance.”
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