It was a result that saw Pompey continue their fine Fratton form and move to the brink of the top six.
But despite a 2-1 victory over AFC Wimbledon on Saturday, the midfielder wanted to see a more ruthless display.
He provided the assist for Marcus Harness to open the scoring during a first half that the hosts totally dominated.
Joe Pigott brought the Dons level after the break, though, before John Marquis headed home the winner.
Cannon said: “The main thing is that we got all three points, although we should have punished them more in the first half.
“We could have scored two or three goals, but couldn’t and that allowed them to come back into the game.
"We just need to be a bit more consistent and hopefully that will be the case in the second half of the season."
“But we found a way to win and although we far by far the better team, you’re not going to be on top all the time.
“Wimbledon were dominant immediately after their goal and had a decent spell of around 15 minutes.
“They made it tough at times – that’s football for you. But we showed the right mentality to end up with three points.
“We do need to start finishing sides off, though, because that’s what the top sides do. You want the game over by half-time.
“There were a couple of great goals from Marcus and John, but we want to be even more ruthless if we can.
“We just need to be a bit more consistent and hopefully that will be the case in the second half of the season.”