Paul Lambert said Villa will "take their medicine and go again" after his side's FA Cup defeat at the hands of Millwall.
Villa took the lead through Darren Bent before Danny Shittu headed the home side level before the break.
John Marquis put the London Lions into round five with just two minutes remaining.
But Lambert insisted there was no time for the team to feel sorry for themselves.
Lambert said: "It's not great, but you have to keep going.
"You take your medicine, pick yourself up and go again. There's no way you can lie down.
"I don't think we deserved to lose it, I didn't see that coming.
"We went 1-0 and conceded a goal from a corner again. It's individual errors that are hurting us at the minute.
"You've got to live with that, you've got to be prepared to be hurt in the penalty box.
"It's not been great but we had a lot of the ball. It's a game I thought neither team was going to win and I thought it was going to a replay."
Lambert felt his side bossed the game but he was frustrated to see yet another set-piece goal come into play during the match.
He added: "I was worried how they were going to react after the other night but they went and took the ball and gave it another go.
"But you can't defend set-pieces like that.
"We bossed it really, with the possession. It's individual errors that are costing us on set-pieces and the second goal was just a crossed ball and we should deal with that.
"I thought we showed grit. I thought we dominated the game and I never thought either team looked as if they were going to win it towards the end."
Lambert rested Christian Benteke and kept Gabby Agbonlahor on the bench with one eye on the big Barclays Premier League clash with Newcastle on Tuesday.
He added: "The lads have played a hell of a lot of games and we've not got the biggest of squads. You have to watch what you're doing.
"You can't make too many changes but the Premier League is the most important thing."
Lambert faces an anxious wait to see the extent of Fabian Delph's injury, after the midfielder limped off in the first-half.