Saints briefly led at Wembley when Finn Azaz crashed in from range before Man City scored twice in six minutes to complete a heartbreaking comeback.
Harwood-Bellis, a product of Man City's academy, admitted there was little Saints could do about Nico González's stunning winner from range.
But there is no time for Saints to mope after this defeat as they face automatic promotion rivals Ipswich Town on Tuesday at St Mary's.
"It's obviously a tough one to take. I thought we dug in really well, but yeah, better quality [won]. The first goal is a bit lucky," Harwood-Bellis told TNT Sports.
Taylor Harwood-Bellis wants Saints to take the positives from their defeat to Man City.Taylor Harwood-Bellis wants Saints to take the positives from their defeat to Man City. (Image: Stuart Martin)
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"But the second one, it's a hell of a strike. It's a tough one to take, but we're proud of ourselves. I felt quite comfortable. Obviously, they had chances.
"We were rolling our luck a bit, but I felt quite comfortable. You know that they've got quality, and he's obviously smashed it in the top corner.
"Sometimes you just cannot stop the quality of those strikes. The box may get out quicker, but yeah, he has a clear shot and just smashed it top corner.
"There's nothing Daniel [Peretz] can do. It's a tough one to take, but we can be proud of ourselves. It's not what we want to be saying after the game."
He added: "I don't like saying that we can take positives from a defeat, but they're Man City, and we've got a lot to play for the rest of the season now.
"We'll knock that on the head and go again on Tuesday. We've not lost sight of what we set out to do at the start of the season, and that's promotion.
"If anything, what we could do in the FA Cup was a bit of a bonus. But we're proud of ourselves for winning games, so losing hurts."