Jansen's late deflected effort earned a 2-2 draw on Bert van Marwijk's debut on the Hamburg bench and although the result may have been a touch fortunate, it was nevertheless a step in the right direction.
"We can build on this," said Van der Vaart. "We fought, we had a bit of a system and we tried to play good football.
"Sometimes it worked, sometimes it didn't. When you score so late on, then you've got to be happy."
Jansen added: "We came from behind twice and were always in the game, and we never fell apart.
"There were games in which we did fall apart and concede five, six or seven goals, but here we had the will to fight back and we got our chances. It was down to our attitude."
Van Marwijk was satisfied with his return to the Bundesliga, although he is aware he has a lot of work to do to lift Hamburg out of danger.
"If we have faith in ourselves, if the team has faith, then I think we can improve," he told Sky television.
"We knew it wouldn't be easy, but in the end, we got a deserved 2-2 draw."