The Hammers have won just one of their last eight Premier League fixtures, and only three of 15 so far this season.
Unsurprisingly, an inability to string positive results together has left them languishing at the wrong end of the table and looking anxiously over their shoulder.
Only goal difference is keeping Sam Allardyce's side out of the bottom three at present, with a 4-1 reverse away at Liverpool on Saturday pushing them a little deeper into the mire.
Jarvis told the club's official website on the need to offer a positive response: "We can't feel sorry for ourselves.
"We need to stay positive and make sure we are working extremely hard, as we did at Liverpool, and get that positive result we need to kick-start our season.
"It's definitely time to roll our sleeves up and fight. That's exactly what we need to do. However we get the three points, it doesn't matter what we do, we just have to get them and get ourselves up the league.
"We will try to do exactly what we did against Fulham when we face Sunderland on Saturday. If we do, then we'll get three much-needed points and hopefully we can do that on home turf."
On the defeat at Anfield, which saw the Hammers hold their own for long periods but concede at important times, Jarvis said: "We started the game well and created some good opportunities and could have gone in front and given ourselves something to really hold on to.
"To concede just before half-time shot ourselves in the foot.
"Of course it was very unlucky but it was disappointing to concede just before half-time, because that always makes thing hard.
"At 2-1 they looked a little bit nervy and we tried to get back level. We had a couple of chances to score and if you don't score in this league then you get punished, and we did."