Kenny Jackett knows Pompey have to start turning their dominance into goals.
His side have controlled their two most recent matches against Gillingham and AFC Wimbledon for long periods, creating plenty of chances.
But a solitary point was collected from those fixtures, with a stoppage-time goal condemning them to defeat at Kingsmeadow on Saturday.
There is a chance to put that right when Lincoln visit the south coast on Tuesday night and Jackett wants his troops to believe in their ability.
The Blues boss said: “Perseverance is key, but we’ve played quite well in our past two fixtures – particularly in the first half.
“We need to keep working hard and play with confidence, backing ourselves to be clinical when we get into good situations. That’s been the message to the players.
“The overall situation at the moment is obviously very disappointing and nobody feels that more than me.
"We need to keep working hard and play with confidence, backing ourselves to be clinical when we get into good situations."
“But we’ve got a really big week ahead and we need continue the things we’re doing well, although the bottom line is results.
“I fully appreciate that the fans are entitled to voice their opinion – and I do share their frustration at the moment.
“We’ve shown some promise in recent weeks, but we need to capitalise on that and make sure we actually get over the line.”
Pompey face a Lincoln side sitting in 12th position following their goalless draw with Shrewsbury on Friday night.
Jackett said: “We don’t just want to have a good start to the game – we want to have a good middle and end as well.
“It will be a difficult match for us, although if we get our own performance right then it’s certainly a winnable one.
“We’ve done our homework on Lincoln and prepared properly, but the important thing is that we improve.”