Hecking's men had not lost in 15 consecutive matches but were unable to overcome fifth-placed Augsburg at the SGL Arena on Saturday, which allowed Bundesliga leaders Bayern Munich to strengthen their grip on the title.
Bayern defeated Hannover 3-1 to stretch their lead over second-placed Wolfsburg to 11 points, but Hecking was more focused on his side's failings than what it meant for the German league overall.
"It was a deserved defeat. We weren't as forceful going forward as we had been in previous games – we were never as present and a lot sloppier too," he said.
"We never managed to put any real pressure on and create chances. In the decisive moments, we weren't alert enough.
"We need to look at our mistakes and the reason for this defeat. We must focus on the tasks that lie ahead now and work hard to ensure we are successful."
Augsburg scored the only goal of the game in the 63rd minute after Wolfsburg defender Naldo brought down Abdul Baba in the penalty area.
Tobias Werner's spot-kick was saved by Diego Benaglio but Dominik Kohr slotted the rebound to secure victory for the hosts - their first in five matches.
While Saturday's loss effectively ends Wolfsburg's slim hopes of Bundesliga success - they have 10 matches remaining to reel in Bayern - Hecking's team remain in contention for the UEFA Europa League and DFB Pokal.
