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The 41-man squad arrived in Auckland on Wednesday, and were greeted at the airport by a traditional Maori welcoming ceremony.
Gatland's side begin their 10-match in New Zealand tour on Saturday against a Provincial Union XV in Whangerei.
"You can't dwell on it," Gatland said. "We know what a daunting challenge we face. Everyone is really up for it."
New Zealand coach Steve Hansen has been the latest to comment on the Lions' brutal itinerary, which includes five matches against Super Rugby sides and three Tests against the world champions.
Former All Blacks boss Graham Henry has described the schedule as "suicidal".
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"I've mentioned how difficult the schedule was for 12 months," Gatland said. "So it's a bit ironic people are talking about it now.
"You can't change it, so if you let those sorts of things worry you it is going to influence the team.
"But those tough games will give us nice preparation in terms of getting us ready for the Test series."
The Lions will spend Wednesday and Thursday recovering from their journey, then hold a final training session on Friday before the tour opener.
Hooker Ken Owens will not feature this weekend as he continues to recover from an ankle injury, but says he will be in contention for the matches next week against the Blues and Crusaders.
The Welshman led the Lions in a rendition of Calon Lan on arrival at Auckland airport.
"We have four choirmasters - one from each nation - and we decided it was the Welsh turn to sing today," Owens said.
"The boys weren't too bad - a work in progress, but a good effort so far.
"It's always a great welcome when we come to New Zealand. It's great to experience some of their culture and give some of ours back."
The British and Irish Lions should not worry about their "difficult schedule", head coach Warren Gatland says.