The Hammers bowed out in the qualifying round of the Europa League while managing only three points from their opening four Premier League games this term thus far, which prompted some antisocial behaviour on the weekend.
The London club were leading 2-0 against Watford after 33 minutes at the London Stadium on Saturday but capitulated to lose the game 4-2, but Noble is urging unity after a poor beginning to life in their new home.
Noble said: "That is the best we have played for a long while, in the first half. A couple of mistakes have cost us and we couldn't recover.
"If we can go in 2-0 up at half-time it is a different game, but the mistakes have cost us in the end.
"There is a long way to go and we have to stay positive."
"We have still got new players coming in learning the league and we have a lot of players in their second season," he said.
"We have got players coming back from injury like Manu and Dimi.
"We have got to take the positives and we played fantastic in the first half, but we conceded silly goals."