Disappointed Horsham manager Simon Colbran admitted his players switched off for 20 minutes after half-time which cost them three points on Saturday.
Horsham led 1-0 at half-time through a goal by Gaby Odunaike on 41 minutes and looked the better side against second-placed Hastings for the whole of the first half.
But they conceded two goals after the break which ended up with them suffering a 2-1 defeat.
Colbran said: “We were absolutely brilliant first half and everyone was doing what I wanted them to do.
I said at half-time you’ve got to do it for 90/95 minutes against good teams.
“Hastings are a good team and when we came back we had 20 minutes where we weren’t switched on. We made some mistakes and they punished us.
“When you are playing the better teams in this league they will punish you if you are not on your game.”