Lee Brown admits Pompey had a frustrating evening against Charlton at Fratton Park.
But the defender is not getting carried after they suffered just a second League One loss from the opening 21 games.
Andre Green’s strike proved no more than a consolation, following first half strikes from Karlan Grant and Nicky Ajose.
And Brown hopes it will be a mere blip for the Blues as they look to get back on track at Barnsley this weekend.
He said: “We had so many chances in the second half, with penalty appeals and shots cleared off the line.
“So it is frustrating, but you do have those games at times – on this occasion things just didn’t fall for us.
"There will be tests for you to face during the season and it’s about how you react."
“Conceding twice in the first half was particularly disappointing because it’s something that we’re not used to.
“That’s 21 games now and you will have bad 45 minutes defensively in a season, whether that’s individually or as a group.
“There will be tests for you to face and it’s about how you react. I thought we did well in the second half and could have come away with something.
“Now it’s done and there’s nothing we can do about what’s happened, so we’ll look forward to Saturday and try to bounce back.”
Brown felt Pompey should have been awarded a penalty for a handball in the second half and was amazed by the decision to send off Ben Thompson late on.
He said: “I always look at how many players around the ball appeal. If it’s one or two, then there’s probably nothing to it, but when it’s six or seven then there must be something. It’s an instant reaction.
“The red card was a crazy decision and because Thommo’s as hard as nails and bounced straight back up, he gets penalised for it.
“If the other guy was up and he was rolling around then the decision would probably have gone the other way.”