The midfielder says his error from 12 yards cost his side a victory of major importance in their last league outing, but revealed he will continue to take spot-kicks
The Dutch midfielder hit the post from 12 yards with his side 2-1 up in the second-half, and they paid the price as Alvaro Dominguex scored a 92nd minute equaliser to rescue a point for the home side.
Van der Vaart had given his side the lead with a spectacular goal but he explained that he was extremely disappointed with his miss later in the match.
"It is really, really disappointing. We would have won if I had scored. I resent it very much," he told Bild.
"If we had not conceded in the last minute, I would not have thought for a second about my little mishap."
The former Tottenham playmaker explained that he will continue to take penalties despite the events of Wednesday night, but says he may now change his training routine regarding spot-kicks.
"Yes, I'm still going to take penalties. I have always practised penalties but maybe I will have to practice even more now," he added.