The Dutchman helped Hamburg escape relegation by the narrowest of margins, after a 1-1 aggregate draw with Greuther Furth in their end-of-season play-off saw them retain their Bundesliga status by virtue of the away goals rule.
That result meant that the club maintained their record as being the only side never to have been relegated from the top flight, and Van der Vaart explained that joining up with the national squad has come at the perfect time.
"It feels like such a relief after such a season with Hamburg," he told Dutch television station NOS.
"If you come to the national team, the level is higher and there players there who have won titles.
"That's why the mood is so positive, I feel really comfortable here."
Dutch coach Louis van Gaal is yet to finalise his 23-man party for the finals in Brazil but should Van der Vaart make the cut it will be his third appearance at the tournament, with Netherlands looking to go one better than four years ago, when they lost 1-0 to Spain after extra-time in the final.
