The Reds were two goals to the good at Brisbane Road but bowed under pressure and enabled Orient to attempt a comeback.
Hourihane lost his first game as Barnsley’s permanent head coach after Omar Beckles scored to seal a 4-3 victory for Orient.
“If there’s one game to sum up the season then it’s probably today,” Hourihane said. “I thought we were outstanding for the first 25 minutes.
“We controlled the ball, played most of it in their half and created chances. Then, as I’ve just told the players in the dressing room, I hated the rest of it.
“I hated the way the team looked. We didn’t string passes together. It became scrappy and we created lots of transitions for them which they’re good at and we didn’t compete.
“At 3-1 I still felt really uncomfortable and the players had lost their way in the game. We gave the ball away a couple of times, so it was from our own downfall why they won the game.”
Hourihane took the reins as caretaker at Oakwell last month, when Darrell Clarke was relieved of his duties.
He led the Reds to an impressive 4-1 win over Bolton Wanderers last week but the loss at Brisbane Road was a stern reminder there is a lot of work to do.
“We need to be braver,” Hourihane said. “I want us to play aggressively but when it became scrappy, I really didn’t like what I saw. We need some fresh new faces around the place for next season.”
