"In this completion i don't think you ever have it in the bag until it's over," said Kearney.
"It says a fair bit about us in the sense that we are our own worst enemy at times.
"The lads showed some real courage to claw their way back like they did and we just lacked the football presence to nail the door shut.
"It's a shed full of heartbroken and shattered players because they did a great deal right out there, we just couldn't finish it off."
The result was the Warriors eighth consecutive loss, equalling their worst losing streak in a season, and they are now in danger of plumbing new depths with one game remaining against West Tigers in Sydney next week.
The defeat leaves a bitter taste in the mouths of departing Warriors Ben Matulino, Ryan Hoffman and Charlie Gubb, along with the 9,167 loyal fans that braved the wet and cold conditions.
Manly dominated the early stages with five-eighth Blake Green kicking two 40/20s before delivering an inside ball for lock Jake Trbojevic to score.
The Warriors struggled to get out of their own half and three poor passes from dummyhalf put them under more pressure before a penalty allowed Wright to extend the Sea Eagles' lead.
The Warriors scored twice through wing David Fusitu'a to make it 8-8, but Manly pushed ahead early in the second-half through another Wright penalty, before Trbojevic's cross-field kick found Walker for their second four-pointer.
Fusitu'a then sent centre Blake Ayshford in to help the Warriors back to 14-14, and Maumalo and Johnson's late heroics appeared to have them on track for victory only for it to slip through their grasp.
Kearney conceded poor options cost his side but refused to single out Maumalo's late run as the error that brought them undone.
"I don't think it was Ken's doing," he said. "The ball shifted out to Ken and he's on the end of the line.
"That's where I'm talking about the football awareness, when you're that close to the sideline on a pretty greasy night it's probably a smart idea to come back into the middle of the field.
"But I'm not going to sit here and blame Ken for the loss, absolutely not. But like I said before we probably are our own worst enemy at times."