Sam Warburton admitted the Lions' lack of discipline proved costly in their 23-22 defeat to the Highlanders.
The Lions slumped to the second loss of their opening four tour matches despite leading 22-13 in the 54th minute, paying the price for conceding 12 penalties to the hosts' five.
"There was a string of four penalties in that second half when we were in decent territory, but we gave away four penalties in a row," Warburton told Sky Sports.
"That gave them way too much territory and momentum and they scored off that eventually.
"Our discipline on Saturday (against the Crusaders)... we kept penalties to single figures and for one reason or another that didn't happen here.
"You have to give the Highlanders credit because they forced the pressure to give away penalties, but we have to keep penalties to single fingers."
Next up for the Lions is the New Zealand Maori, live on Sky Sports on Saturday, and Warburton says it will be their toughest test to date.
"The Maori game is going to be the biggest game we have had so far on this tour," Warburton added.
"They have picked a great squad - a lot of guys with All Black experience. We are looking forward to the challenge and it is going to be a really big game for us."
Up next the British and Irish Lions take on the Maori All Blacks in Rotorua on Saturday, with the action kicking off from 8am on Sky Sports 1.