Omar Bugiel’s goal at the death completed Bromley’s comeback in the five-goal thriller after the Wood had taken a two-goal lead thanks to Morgan Ferrier’s double.
A win would have moved Garrard’s side up to fourth and made their play-off place safe but they now go into the final day needing a win to make sure.
They host bottom club Guiseley and the Wood boss wants his side to improve at both ends of the pitch before the play-offs.
“I felt all three goals were disappointing from our point of view,” Garrard told Boreham Wood TV.
“We had six to eight goal chances and we didn’t put them to the sword. In both 18-yard boxes we failed.
“We were 2-0 up away from home. You can’t come away from home needing four goals to win a game of football.
“There are so many frustrations on our part. Had we won, we would have nailed down our play-off spot. Finishing four or fifth is out of our hands now.
“Football kicks you in the proverbials. To be fair to Bromley, they were the ones that wanted to go and win the game. Our game management was poor.”
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