His side defeated Leeds Rhinos 14-13 after Lee Gaskell’s drop-goal with the final play of the match.
Watson, who took over in November, had seen his side fluff a number of opportunities against their West Yorkshire rivals.
Giants had also made a habit of losing narrow games last year as well as this term when they fell 25-24 at Hull KR.
“It feels good,” said Watson.
“It was a sloppy one and tough but a win’s a win and it’s important to get off the mark.
“When Liam Sutcliffe’s drop goal comes off the crossbar to put them in front I did think it’s one of those days.
“We were very, very edgy and you could see that. We looked like a side that had lost some games by a point.
“I tend to keep my emotion out of it, though. I’m looking at our processes. I know it should have been more comfortable.
“We’d a couple of tries ruled out and there were a few calls there that I don’t want to go in to. But it’s good for the boys.”
Leeds were missing 11 players but coach Richard Agar was not happy as they suffered a fifth straight loss.
“I am disappointed in the way we shot ourselves in the foot during the game and the way we managed it,” he said.
“I thought we were in a good position at half-time, but in the 10 minutes after the break we have got some experienced players who have come up with some really poor errors.
“When you’ve got as many players missing as we have, we need more from those experienced guys. It’s just not good enough.”
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