The PSG coach took off both Ousmane Dembele and Khvicha Kvaratskhelia at half-time of their opening game of the new Ligue 1 season, bringing on Mika Godts and Ferran Torres, who scored twice to salvage a point at Stade Rennais on Sunday.
"Football is like that. Paris Saint-Germain have won nothing, nothing," he said of the new season where they defend not only their Ligue 1 title but chase a third successive Champions League victory.
"If you think about what you've won, you're not going to win anything! There is no credit. You have to show every day, every match, every training session, that you're ready. Otherwise, it's easy to relax and start slipping.
"I wasn't brought up that way. We are always looking to win, and to keep winning, you have to step outside your comfort zone. Is that clear?"
PSG, who won the European Super Cup this month but lost the French version to Racing Lens, played a sluggish first half at Rennes and were 2-0 down at the break.
But new Spanish signing Ferran Torres, who netted the winner in last month's World Cup final, came on for Dembele and scored twice to ensure a point for the Parisians.
"He wasn't bad, was he? He scored two goals, but I'm happy with everyone who came on in a very difficult match because we had a lot of trouble controlling Rennes in the first half," Luis Enrique said.
"They were good on the counter-attack and scored two wonderful goals. It was complicated, but it's important for me to see that so many players are ready.
"We sign players to go on a long journey with them. It's very positive for him and we're very happy," he said of Ferran Torres' debut.
"We're always looking to find the best players for every match. Places in the team will be more difficult to get than last year, and that's our ambition.
"I think we had a very good transfer window, and we're still open to different possibilities. Everyone knows how difficult it is for a team to keep winning. And clearly, we still need to improve."