The Magpies had exited the Premier League relegation zone for 38 minutes following Allan Saint-Maximin’s opener at St James’ Park.
However, Joao Pedro’s equaliser on 87 minutes at the Gallowgate End saw United waste their golden opportunity.
They now sit two points adrift of safety, while the Hornets, in 17th place, also have two games in-hand.
Old habits die hard for Eddie Howe’s side, who have dropped an astonishing 21 points from winning positions this season.
‘We made a couple of errors’
“Yeah, I’d say so,” Howe said, when asked if that statistic was his side’s major down at present.
“Our performance, up until our goal, was very good and then I thought as soon as we scored, we went into a different way of playing,
“I thought our press dropped and we became deeper on the pitch and invited pressure.
“Not that I think Watford created too much pressure, I thought most of their opportunities came from our individual mistakes.
“But still, I felt we brought them into the game and the goal typified that where we made a couple of errors.
“At this level, that detail matters and we’ve ultimately conceded and it’s cost us the match.”
‘It is particularly damaging to us’
Indeed, had Howe’s men held on for three points, they would have leapfrogged the Hornets ahead of the visit to Leeds United next weekend.
“It is particularly damaging to us because this was a chance to beat a direct rival,” Howe said.
“We were 1-0 up with minutes to go, it is even more of an opportunity.
“We know that we have damaged ourselves to a point, but you always have the opportunity to bounce back from that.
“The games don’t get any smaller, they get bigger with every match.”