The Dutch beat Poland and shared a goalless draw with France as Inter Milan's Stefan de Vrij paired captain Virgil van Dijk at the heart of defence.
Bayern Munich player De Ligt had hoped to start and said ahead of their clash with Austria on Tuesday he had spoken to a psychologist and his family.
"These kinds of moments can be tough, by talking about it you make things lighter and you can put the energy back on the pitch instead of wasting it on those kinds of thoughts," De Ligt told Dutch media.
"I always train to improve myself, that is not necessarily different now -- what is a little different is the feeling after a victory.
"Of course you are also happy as a substitute, but a little less than if you had participated yourself."
Liverpool defender Van Dijk admitted he needed to improve after the team's 2-1 comeback win in the opener against Poland, and the defence held firm in a solid second outing against tournament favourites Les Bleus.
De Ligt, 24, started for the Netherlands in their opening game of the 2022 World Cup but was dropped by then-coach Louis van Gaal as the Dutch reached the quarter-finals.
"I had the feeling that I was in good shape, and I showed that at Bayern in the second half of the season... I would have liked to continue in that line here, in that sense it is a 'false start' to the tournament," said De Ligt.
"I have learned during my football career that the start of a tournament or season is fun, but that it is mainly about the end.
"That's why I'm relatively calm. I also have the feeling that something will happen this tournament that will allow me to still be important... you have to be ready for that."
Netherlands striker Wout Weghorst said he could personally "see the beauty" of being a super-sub, after he came on to score the winner against Poland, but also would like to start.
"The way the first match went is nice and you get satisfaction from that," the Burnley striker told a news conference.
"But I said it at the beginning of the tournament -- you want to be in the starting line-up."
Netherlands are guaranteed to reach the last 16 with at least a draw against Austria.
