They lost 20-10 against Catalans Dragons and finished with 12 men after Joe Greenwood’s red card for a high tackle on Samisoni Langi in the 76th minute.
It followed Sunday’s opening day defeat against Hull FC and - still without injured captain Aidan Sezer - left Watson with plenty of issues to contend with.
They were 6-0 down early on against Catalans, who were inspired by England full-back Sam Tomkins, and were 20-6 down by the break.
Chris McQueen scored for Giants who saw Sam Wood add their second try just before the hour but they could not wear down the France side any further due to a mixture of poor execution and some excellent defence.
Watson conceded: “In the first half we didn’t give ourselves a chance on back of ill-discipline.
“The second half taught us a lesson. We were loads better.
“We’ve learnt that lesson now but it shoudn't take us to come in and have to learn it like we did.
“If we’d not conceded that stupid (Mike McMeeken) try at half-time and the Jermaine (McGillvary) try was scored as well, it’s a different game.
“It will click at some point. It’s building the process and mentality into the players. We’re not a million miles away.”
On Australian scrum-half Sezer, Watson added: “Aidan’s had a bit of a setback.
“He trained on Wednesday and got through the majority of the session but felt a tweak at the end.
“He’s had a scan and it’s come out he’ll be missing a couple of weeks more.
“You do miss someone like Aidan - but the team today was still good enough to win.”
Watson did not want to comment on the Greenwood red card.
But he thought the stop-start nature of the game due to blood stoppages was “bordering on ridiculous” after play was halted for Catalans centre Dean Whare to have his bloodied shirt replaced and likewise with Jason Baitieri as well as other stoppages for cuts.