The Gulls were on top for much of the first half, but failed to make it count and Matt Richards' 75th-minute goal kept Cheltenham's play-off hopes alive.
"In the first half we were the better team, but in the second half we made the slight slope here look like a mountain," Hargreaves said.
"We had a few good chances, should have been in the lead but we didn't score when we were on top.
"We weren't on the front foot enough in the second half and the players know that.
"Luck is a deflection off the floodlight and the referee's head, not failing to be tight from a second ball, which was bad play for their goal.
"In the second half, in both boxes we were dominated, so I am disappointed with that performance.
"Cheltenham were a team waiting to be beaten for me, but we didn't and I am really annoyed."
Veteran Cheltenham striker Jamie Cureton missed from a good position after half an hour, skewing wide of the near post.
Jermaine McGlashan opened up space for a shot which was also off target, but Courtney Cameron should have done better for Torquay in the 40th minute, lifting an effort over the crossbar.
Torquay goalkeeper Martin Rice was called into action for the first time in the 41st minute, parrying Cureton's shot and during time added on, Vincent kicked Shamir Goodwin's effort off the goalline.
Rice denied Vincent with his legs, but the deadlock was broken 15 minutes from the end when Vincent's long throw fell to Richards just inside the box and he connected well with a left-footed volley into the bottom right corner.
Brown saved from Goodwin as Torquay tried to salvage a point, but Cheltenham held on for their fifth home victory of the season.
- Sports & Recreation
- Ashley Vincent
- Matt Richards