The 67-year-old was pleased with the way his side fought back from behind twice to beat Fortuna Dusseldorf on Saturday
Jerome Boateng scored the dramatic winner with his first Bundesliga goal in the 86th minute on his 130th appearance in the German top tier.
Mathis Bolly opened the scoring for the visitors before Thomas Muller equalised on the brink of half-time, but an Andres Lambertz strike made it 2-1 to Dusseldorf, only for Franck Ribery and Boateng to turn the game around for the league leaders.
Heynckes believes the game proves why complacency must be avoided, and refused to acknowledge that the title is in Bayern's hands despite Borussia Dortmund's 2-1 defeat to Schalke this weekend, which leaves the Bavarians 20 points clear at the top of the table.
He told reporters at the press conference after the game: "Today's game showed that we have not won games even before the kick-off.
"The team twice came back from behind and showed great morale.
"As long as we are not mathematically German champions, we will not accept congratulations."
Bayern face Arsenal at the Allianz Arena on Wednesday night in the second-leg of their last-16 Champions clash, with a 3-1 lead from the first leg.