Jermaine Beckford's goal condemned the struggling Tykes to their fourth successive defeat in the Championship and extended their winless home record to six games.
"It's not about the performance, it's about the result," Hill said.
"Again, the performance was lacking penetration and I think it's obvious to everyone why we're not winning games and we're losing games. I just want to focus on one thing and it's definitely the result.
"The players are suffering with a lack of confidence. It looks like that, but we've got to pick them up and they've got to pick themselves up. We've got to play with that self-belief; that energy.
"I'm not too disappointed about the performance; it's a results driven business. The players have got to accept the challenges and have got to be able to express themselves with a freedom and no fear.
"They've got to forget about the pressures of the situation. The brain is the athlete and sometimes it plays tricks with your ability and I think we witnessed a little bit of that today."