The Hornets missed the chance to climb up to second in the npower Championship after Burnley sub Sam Vokes pounced on a slip by Matthew Briggs at the back to secure a 3-3 draw in stoppage time.
"I thought we'd done enough,"' admitted Zola. "We came back from behind twice and then went ahead and towards the end I didn't see that coming but it's not the first time that has happened.
"A sloppy piece of defending costs us a lot. I understand we have a very young team but there's not much time for them to learn, we need to grow up quickly.
"We have done very well so far and it would be a shame not to finish what we have done.
"It was a pity because Briggs played a good game. This time it was him but other times it has been someone else. Now is the time we cannot give anything away, every single game is going to be very difficult."
Watford could have leapfrogged Hull into second with a victory but instead the Tigers will be four points clear by the time the teams meet on Tuesday if they beat Huddersfield.
Charlie Austin prodded Burnley ahead after only 39 seconds but the lead lasted just five minutes before Troy Deeney curled a fine leveller.
Austin took his tally for the season to 28 in the 24th minute, smashing in a penalty after Marco Cassetti tripped Alex Kacaniklic. But once again Burnley let their lead slip within five minutes, this time when Fernando Forestieri jinked inside Jason Shackell and rifled an angled shot past Lee Grant.
Forestieri thought he has won it for Watford with a 72nd-minute strike from the right-hand corner of the area but instead Vokes made it a happy return to Vicarage Road for Sean Dyche.
- Sports & Recreation
- Matthew Briggs
- Sam Vokes