Jon McLaughlin says the Sunderland squad are determined to win promotion for the club's supporters.
Over 40,000 travelled to the capital for the Checkatrade Trophy final and with the Black Cats 1-0 up at the break, it looked like being a famous afternoon.
It ended up in penalty heartbreak and the Scot says they must bounce back.
"I'm sure all the players will tell you that this will hurt more because we know how much it will hurt for the fans," he said.
"Personally you want to win the trophies but knowing the support we had today, how much it meant to them, to travel down to Wembley with that feeling that things were going in the right direction again, I'm sure it's going to be really, really tough for them.
"It's really disappointing that we couldn't produce that bit of magic of them, but we've still got a lot to concentrate on and we've still got a chance to give them a much bigger reason to celebrate.
"We've got to focus now, it hurts now but all we can do now is get this club promoted," he added.
"The support has been incredible and that's why it's even tougher to swallow.
"The scenes that we could have given everyone on Sunday night. That's hard for everyone to take on, all we wanted was to give them a reason to go mad again.
"Now we've got to look to the next opportunity, Wednesday night at Accrington, to get that positivity back.
"You've got to move on quickly, put it behind us.
"We'll look back on this and what could have been, but we've got to move on and give the fans something to really cheer about by getting promoted."
McLaughlin suffered a frustrating shootout, getting a hand to Portsmouth's first effort but just unable to deny Gareth Evans.
The rest of the Pompey penalties were excellent and left Sunderland to digest a narrow defeat.
"It was almost too poor a penalty, you've gone full stretch and it sneaks underneath the body, it's frustrating because that would give us a great chance," McLaughlin said.
"At the end of the day, you do your homework, work on things but out there it's a flip of a coin, it's fine margins.
"It's disappointing not to be able to save one for the lads and for the fans but that's what happens sometimes.
"It's a very bitter pill to swallow, losing a cup final in those circumstances.
"You've got that chance of glory, the lads have put in a great performance but we've come up against an equally good Portsmouth side.
"You can see in the league table how tight things are between us.
"It was a game of two halves, both teams had chances at times, it was very evenly matched and could have gone either way."