After falling to behind Sam Winnall’s goal, PNE equalised in the second half with a fine debut strike from Aiden McGeady.
But with them looking the better side after getting on level terms, North End were undone on the counter-attack with 10 minutes left as Newcastle United loanee Alan Armstrong netted for the visitors.
Lilywhites boss Grayson said: “If anyone was at the game they would have seen how well we played, especially in the second half.
“I thought we absolutely dominated the ball, the chances and the opportunities in the second half, we limited Barnsley to hardly anything.
“Then to be hit by a sucker punch on the counter-attack is very difficult to take for everybody – for the supporters, the players, the management - again, we didn’t deserve to lose that game.
“Unfortunately we have and that’s football sometimes it can be cruel to people at times.
“We will keep believing in what we are doing, keep working hard and eventually the breaks will come for us.
“At times we played some really good stuff, created some good opportunities but weren’t ruthless enough in that box.
“We had some good opportunities to win it and then you saw Armstrong go up the other end, do his bit of magic which was the difference between them winning the game and us not getting anything out of it.
“This is a ruthless division and we have to make sure we stick together.
“We know we have an honest bunch of players who will get a scrappy win at some point and we can kick on, I am very sure of that.”
Grayson gave debuts to the three deadline-day signings, McGeady, Alex Baptiste and Marnick Vermijl.
He admitted that strikers had been enquired about too in the build-up to the close of the window, included Barnsley’s match-winner Armstrong.
“We enquired about a few different players, we enquired about Armstrong at Newcastle but we were told he could only go to a newly-promoted club,” said Grayson.
“There weren’t a great deal of strikers out there who you would say could come in and improve us.
“That just wasn’t on deadline day, it was in the period leading up to it.
“We think we have some decent players who aren’t firing on all cylinders at the moment but they will do.
“What we did was to bring in three players who we thought could improve us.
“Alex Baptiste was outstanding out there, Marnick Vermijl did a good job going up and down, McGeady showed glimpses of what he can.
“The three made an impact and will get better.”
Grayson was asked about criticism on social media from supporters after five defeats in the first six Championship games.
He said: “If they are fed up, don’t come to the game.
“We are working our socks off to make sure this club does everything in its capabilities to make sure it keeps progressing.
“If anybody has been to every game this season so far, they will realise that we have been in every game – we have never been out of any games.
“The games we have lost have been by the odd goal, that is not a team struggling for confidence, not a team hanging in games and getting battered by four or five goals.
“If we were getting beat by fours and fives then we have a problem, but we are nearly there.
“Things will turn and I have faith in the players.
“Social media place can be a cruel place, I don’t bother with it.”
North End are back in action against Cardiff City at Deepdale on Tuesday night.