United wrapped up their U.S. tour with a 3-1 win over rivals Liverpool in the International Champions Cup final in Miami on Monday and after defeating Real Madrid on Saturday the mood among Van Gaal's squad is buoyant ahead of their Aug. 16 Premier League opener against Swansea.
"It was a good tour for us, a good two or three weeks trying to get ready physically and mentally while trying to adapt to the new system," Mata told ManUtd.com. "Obviously, we didn't lose a game which is good for the confidence but the most important thing is that we believe in what we are doing.
United played in front of huge crowds in the United States with 86,000 watching them beat L.A. Galaxy in California and a massive 109,000 in Michigan for a 3-1 win over Real Madrid as the club proved once again their global popularity.
"We take home a lot of love from the supporters. It was amazing from the first day until the last - in every stadium, in every training camp and in every hotel. I think (the highlights were) the support and obviously the new ideas that the manager has brought," said Mata.
Van Gaal's 3-5-2 formation has seen Mata, who scored a well-taken goal against Liverpool, employed in an advanced playmaker role and that appears to suit him well.
"I feel good and I feel comfortable in this position. I have to do what the manager wants me to do, both offensively and defensively, and I am trying to do that. It can be a good position for me to try to perform to my best," he said.
After a disappointing seventh place finish in the Premier League last year under David Moyes, United will be expected to be back in the title hunt and, at the very least, ensure a return to the Champions League with a top four finish.
"We are all excited to start the new season," said Mata, "Everybody wants to do better, we want to fight for the trophies and this club deserves that. We will try our best."
Forward Wayne Rooney, who also scored against Liverpool, gave his backing to Van Gaal's approach.
"He is a tough but fair manager. He has been great since he has come in and he has given us all a different way of looking at football that we didn't have before. So it's been great for us and hopefully that will continue," he said.