"We need to win this match tomorrow, that will be our mindset", Ten Hag said a pre-match press conference. "We have to stick to our own strengths."
Ajax upset Real Madrid and Juventus on their way to the semi final with a fast, attacking style of play, and initially dominated Tottenham in their 1-0 away win last week.
But the Dutch team, which features several players polished in the club's famed academy, struggled in the second half in London as Tottenham increased the pressure on their defence.
"Our minds were a bit too much on defending the lead", Ten Hag said. "But it was also a show of strength by Spurs. It showed we have to cross another frontier tomorrow. But we are confident we can do it. We are fit and we are eager."
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Ten Hag said his team had no injuries following Sunday's Cup Final win against Willem II Tilburg, although it was not yet clear whether Brazilian forward David Neres could start the match.
Ajax's first domestic cup win since 2010 did not interfere with preparations for Wednesday's match, the coach said.
"The players were happy, but you could see they immediately turned their focus to Wednesday's match. Everyone knows what this is about."
Four-time European champions Ajax are looking to reach their first Champions League final since 1996. Many pundits have suggested it has become impossible for Dutch teams to compete with their much wealthier English, Spanish and Italian peers, but Ten Hag is ignoring them.
"A few people who knew this level of success said it would still be possible for a Dutch team to reach the Champions League final; people like Johan Cruijff, Louis van Gaal and (Ajax director) Marc Overmars", Ten Hag said.
"It's up to us tomorrow to prove them right."
Ajax defender Daley Blind said he had never expected his return to Ajax last summer, after four years at Manchester United, would turn out to be so exciting.
"The team has grown tremendously in many aspects this year", the 29-year old son of former European cup winner and Ajax captain Danny Blind said.
"This really is a team effort, and I am proud to be part of it."
(Reporting by Bart Meijer; Editing by Hugh Lawson)
