The Oranje led through Kevin Strootman's opener, but Cristiano Ronaldo pegged them back three minutes from time.
That left Van Gaal with mixed feelings about his side's showing.
"In the first half we created as many chances as Portugal did," he told the media afterwards.
"We created a goal and I cannot say anything about the first half.
"But after the break we had possession and played very badly. We could not hold the ball and we saw the candle going out with some of the guys."
The veteran tactician did take some positives, though.
"If you do not lose against teams like Germany, Italy and Portugal, you are doing it right," he added.