The Saints are in serious trouble in the Premier League after promotion last term.
Despite not having a win in the Premier League so far, Harwood-Bellis wants everyone to remain calm.
He told the Daily Echo: "We started well but our reaction to the goal was not good enough. Then we came out in the second half and we played how we wanted to play.
"We were a team that we wanted to be. We hurt them, and we look more like a team, more of a threat, and we defend properly.
"As you see, we didn't concede in the second half and we scored a goal. I think that just shows that we take our foot off the gas and when we come off it a little bit, we get punished.
"It was a quick free kick. I kind of turned my back and he's done that. That's what happens in the Premier League.
"As I said, you switch off for a second and you get punished. I think it's the quality of it. Obviously, for us as a team, that's not good enough, the reaction.
"But as I said, we come out second half and put the performance in, and do what the manager's asking us to do.
"You see we can win games. We've just got to look at that first half coming together as players. It's not a reflection of the manager or the staff.
"That's far from what we want for them. That's not them, they give us everything. So, to come out, it's hugely disappointing and frustrating to show that that's what we put out."