Centre Adam Warren and back row Nic Cudd grabbed tries for the region, but clinical Saints comfortably wrapped up a 48-14 win on home soil.
Jackman admitted the final scoreline had been hard to stomach and insisted Dragons now needed to stay strong as a group with a trip to Clermont next weekend.
“It may seem strange but it was actually an improvement on last week (against Leinster), which is hard to admit,” said Jackman.
“We had more of the game and they were obviously the better side, but the scoreline was pretty harsh.
“We had a weaker squad on paper and then lost Hibbs (Richard Hibbard) and Ollie (Griffiths) and (Harrison) Keddie during the game, who are leaders for us.
“The boys who came off the bench made an impact and they all put in a massive shift, it’s just against teams like Northampton it’s seven points when you make a mistake.
“It’s hard with the effort we are putting in, but if we don’t cut out the individual errors we get further behind on the scoreboard.
“We kicked to the corner six times in the game and only scored from the last one. If we make the decision to kick to the corner we need to convert those chances.
“We don’t have the power that Northampton had with the likes of Luther Burrell, Taqele Naiyaravoro, Api Ratuniyarawa – they were just getting over the gain line and more.
“We need to be more clinical from the set pieces. But the big thing is that the boys stick together, we work really hard and make less individual errors.”
