Horsham captain Sam Attfield said their batting fell just short of what was needed to beat Brighton & Hove on Saturday.
They suffered a home defeat by 12 runs after being set a target of 164 by the visitors.
Brighton made 164 all out in 48.2 overs with Alasdair Wilson topscoring with 38 and Lachran Sperling hitting 35.
Horsham strike bowler Travis Muller took 3-24 and spinners Michael Munday (4-49) and Will Beer (2-27) were in good form.
Attfield said: “It was disappointing because it was a close match and we just didn’t bat well enough. Just a few more boundaries from the players who did get in would have done it as it was very close.
“We need to get back to a winning mentality.
“We bowled very well with our striker bowlers performing well.”
Horsham batsmen Beer (32), Craig Gallagher (31), Attfield (23) and Kamau Leverock (21) helped them make 152 all out from 45.3 overs in reply.
Horsham make the short trip to local rivals and league leaders Roffey this Saturday.