"You can only get on with it by working hard; we are disappointed but it is only one game and we have to keep that in mind and keep going," he insists.
"We are sixth in the league and we can still get up there; we are playing some of the top teams coming up and we can get back up there.
"You can't have any sort of defeatist attitude - no chance.
"We had the best defence in the league until Saturday and that is something we have got to look at but we could do with keeping 11 men on the field as well."
Christian is now away on international duty with Scotland, as is Don Hutchison - both of whom were watched by Berti Vogts on Saturday - and he admits:
"Ideally we would all be getting sorted out on the training pitch but there are a few boys away."
At least Christian, who will win his 50th Scottish cap against Holland on Saturday - he already holds the world record for U21 caps, having amassed 34 - has something to take his mind off the defeat at Upton Park.
But he does admit he is shellshocked about the loss and adds:
"It was really disappointing, obviously; what can you say, it was embarrassing.
"To think we were cruising at 3-0 up, we couldn't believe it was 3-2, and then to have Jermain sent off it was backs to the walls after that.
"We had had the game totally in control but even the last two goals didn't have to be created - we just more or less did it ourselves and now we have to bounce back."
As for the first goal on Saturday, Christian admits:
"I thought David James was coming for it, he thought I was going to clear it, and the guy has nipped in, so that is something to sort out.
"The second goal was some strike and it has probably dug them out of it a bit because even at 3-1 they were out of it and it gave them a new lease of life as did Jermain going off.
"It was a bad day for us and a great day for them."
Regarding Jermain's sending off, which West Ham are appealing against, Alan adds:
"As for whether Jermain connected, I don't know but I hope not because then he will get his ban lifted which will be a big boost for us.
"But obviously that is for the video panel; to be honest though we could have done with him on the pitch.
"We just kept the one up and tried to hit them on the break a little bit but Brian was unlucky with his own goal and then they scored the fourth.
"They weren't even creating much against us, we just dug a hole for ourselves really - and that is what we are disappointed about."