Ben Close believes it is important for Pompey to finish the regular season on a high.
Defeat to Peterborough means that automatic promotion is now out of their reach with one game remaining.
But the Blues can still secure third spot, which would mean the second leg of their play-off semi-final is on home soil.
So Close wants them to quickly forget about any frustration and try to bounce back against Accrington on Saturday.
The midfielder said: “It’s very difficult. We were looking to get the win and put the pressure on the two teams sitting above us.
“But it wasn’t to be, so we’ve got to get our heads down, work hard and get over the disappointment quickly.
"We want to finish third, which is a big improvement on last season and that’s something we’re always looking for."
“It’s important for us to have a positive performance and result at the weekend and then take that into the play-offs.
“We had a bad blip midway through the season, which was unfortunately longer than ones that Luton and Barnsley have had.
“Now we want to finish third, which is a big improvement on last season and that’s something we’re always looking for.”
Close netted his eighth goal of the season against Posh in an eventful contest that saw them battle from behind before losing 3-2.
He said: “We showed character to get back into the game and could have gone on to win it. Perhaps we did throw too many men forward and that’s something to look at.
“The attitude from the lads was first class and with the atmosphere the fans created, you can see how much they can help us now in the play-offs.”