Andy Hessenthaler admitted the Dover dressing room was like a morgue after the last-gasp 2-1 home defeat to Gateshead on Saturday.
Only 30 seconds of stoppage time remained when midfielder Greg Olley glanced home Gateshead's winner to give the visitors their first win in seven National League games.
Kevin Lokko's eighth minute header had put Dover ahead and Whites held onto that lead until the 78th minute when they failed to deal with a short corner and Fraser Kerr levelled.
Boss Hessenthaler said he sensed the game was fizzling out at that stage, and described Olley's injury-time header as 'a kick in the teeth.'
The defeat – in the division's sole fixture – was only Dover's second in 12 league matches and ended a six-match unbeaten run at home, leaving them in 19th.
Hessenthaler said: "The dressing room was like a morgue afterwards, the boys were all very quiet but that's because they care.
"They were devastated they haven't got something out of the game, they deserved something out of the game.
"There wasn't much in the second half, we made an adjustment, we went to a three (at the back) to try and match them up.
"They had one chance from a throw in out wide when the lad got in and had a shot and we've had a shot with Bobby Joe Taylor when their keeper made a good save, but the (Gateshead) goals are disappointing.
"The first one's from a set play after the young lad (Dover full-back Danny McNamara) has tried to head it to back to the keeper and it's gone out for a corner, but did we deal with the short corner? No. Did we deal with the cross going in? No.
"We need to see it again, to see who's doing what, but then the game was fizzling out.
"You'd take a point in the end, you certainly don't lose the game, and in the end to lose was criminal really."
Dover had started the game superbly, creating several chances and Hessenthaler said he always felt they needed to capitalise more when they were on top.
He added: "We needed that second goal. For all that pressure we had early on, we got the goal but we probably should have gone on and had we got that second goal the game might have been different.
"But give them some credit they kept plugging away. I felt comfortable second half, we did not really look in any danger.
"Yes they had some spells with the ball, because they're good footballers but we never really looked in any trouble.
"To lose the game is heartbreaking for the boys because they put enough effort in and they've been doing that but that's football.
"You get kicked in the teeth sometimes, we've kicked teams in the teeth when we've scored late on but we can't let it affect us that's what I would say. We've got to deal with that and show some character."
Victory over Gateshead would have lifted Whites to 16th – six points clear of the relegation zone – but Hessenthaler said it's no good reflecting on what might have been.
He said: "I think everyone was aware of that and sometimes that affects you on the pitch because you tense up, you're desperate to do well.
"I'm not saying that's what happened but we were desperate to keep our run going and unfortunately we've come unstuck today."