The Dutchman was thrilled his side were able to grind out a result after the tiring international break, although Toni Kroos feels they should have won more comfortably
Mario Mandzukic put the Bavarians in charge early on, but Pep Guardiola's men failed to build on their lead as they laboured in front of the opposition goal, and Robben believes the victory was crucial given the exploits of a number of players during the international break.
"The games when players come back from international duty are always difficult," the 29-year-old told AZ.
"One's travelling from South America, one from Asia, but they can only train on Thursday, then just a bit on Friday.
"The players had a little break, but the ones you notice are the ones who aren't at 100 per cent. But you have to go on, and wanting to win a game is a mental thing.
"At the start, the most important thing is to win games. A 1-0 is always tight. We had enough opportunities to make it 2-0. If you don't, then it stays tight until the end."
Toni Kroos was also thrilled at the result, but acknowledges his side could well have been made to pay for their profligacy.
"We all know it’s never easy in Frankfurt, because they’re a very good team," he told the club's official website.
"However, we still dominated the game for the full 90 minutes. We let them have very few chances, but we have to point the finger at ourselves for not wrapping it up much earlier.
"It would have been a lot calmer at the end."