Steven King admitted his Whitehawk side failed to hit their own high standards as they missed out on promotion to the National League next season.
The Hawks were beaten 2-1 after extra-time by Boreham Wood in the promotion final at Meadow Park.
Lee Angol gave the hosts a 65th-minute lead with a free-kick but Sam Deering levelled from the spot with nine minutes to go.
Junior Morias fired Boreham Wood into the fifth tier with a sweet strike from inside the area two minutes into the first period of extra time.
King admitted: "We were not good enough on the day. It was a poor game and I thought it was going to go to penalties.
"I couldn't see either side winning it and I don't think either side probably deserved to win it as it was about even. But it was a poor game."
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