Anton Walkes says Pompey are hurting after seeing out 2019 with a defeat at MK Dons.
They looked in control for long periods of the Buckinghamshire contest, only to concede two goals late in the first half.
The hosts added a third after the break, with a stoppage-time effort from Ronan Curtis proving no more than a consolation in a 3-1 loss.
It came after successive home wins over high-flying Ipswich and Wycombe, and Walkes knows they have to bounce back at Gillingham on New Year’s Day.
The utility man said: “It was very flat after the game, especially because of the previous two performances that we produced.
“We felt like we were picking up a bit of momentum and ending the year looking strong, so this result definitely hurt us.
"It was very flat after the game, especially because of the previous two performances that we produced."
“There was a period when we were on top and that’s when we needed to take the lead because we had a lot of chances.
“MK Dons were able to capitalise when we lost our concentration and switched off a bit – we were chasing the game from that point.
“We still felt like we were in the game at 2-0 down and it was all about who got the next goal. They were able to do that to kill us off. It’s a hard one to take.
“So we need to get our heads around improving on that and trying to get a better result at Gillingham.”
Injuries to Lee Brown and Brandon Haunstrup mean that Walkes has filled in at left-back and he looked particularly impressive at Stadium MK.
The 22-year-old said: “Whenever I get the opportunity, I’m going to try my best to improve and keep working as hard as I can.
“I was pleased with the previous two games because we managed to keep a clean sheet, but I’ll look back on this performance and see where I can do better.
“It’s difficult with so many matches at this time of year. There are no excuses, though, and you have to get through it if you want to be a professional footballer.”