Sean Raggett has helped Pompey secure a second clean sheet in the space of a week.
But the defender was frustrated that they could only follow a midweek success over Burton with a goalless draw at Lincoln.
A late flurry of chances meant the Blues had the chance to turn one point into three, with Colby Bishop and Ronan Curtis both going close.
And despite his annoyance at the final score, Raggett was pleased that they kept fighting until the final whistle.
He said: “All the boys are really disappointed and that tells a story because I thought we’d done well enough to win the game.
“We had some good chances and it was just unfortunate that we couldn’t put any of them away, but you have those days.
“We kept going right to he very end and probably created some of our best opportunities in the closing stages.
“That happened on Tuesday night and we got the winner, so it shows the spirit we’ve got in this squad. We never give up.
"All the boys are really disappointed and that tells a story because I thought we’d done well enough to win the game."
“There are some good finishers at this club and so I was backing us right until the end to get that goal, but it didn’t happen.
“That’s two clean sheets in a row and we can definitely take the positives from that – we were solid and limited Lincoln.
“They couldn’t really play through us much at all and were looking for the long ball. That’s because of how we defended from the front.
“Everyone’s hurting because we wanted to win, but we’ll take the positives from the game, while also looking at the negatives and how we can improve.”
Raggett recently celebrated becoming a father, with his partner giving birth to their baby daughter last week.
He said: “I don’t really know how to explain it because it’s like nothing else I’ve ever experienced, but it’s been class.
“There have been quite a few babies born this season and a lot of people have been giving me a few tips.”
Raggett received a warm welcome from the Sincil Bank faithful, with his return coming six years to the day since scoring the winner at top-flight Burnley to send the Imps into the FA Cup quarter-finals.
He said: “I didn’t ever realise until I received a few Tweets, so it’s a nice day to come here and play. I had some good times at Lincoln and always enjoyed playing for the club.”