The draw against St Kitts and Nevis on August 24 drew the curtains on India's nine-match winning streak.
And Constantine said the team has learnt valuable lessons from the encounter ahead of the away match against Macau.
"The game against St Kitts and Nevis was a wake-up call for us. We made a mistake in defending a corner and we paid for it. To me, it was a lesson learnt as we need to be more focused and determined," said Constantine.
"What I mean to say is that you won't get that many chances against Macau. So we need to be on our toes," he said.
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Constantine said India has "healthy respect" for Macau and their main aim would be to finish off the game.
"Let us not forget that they will be playing at home and in front of their home crowd and like all other teams, they will be playing to win at home," the India coach said.