West Ham manager Slaven Bilic slammed his team's poor discipline after they scraped through in the UEFA Europa League on Thursday.
The Premier League side battled past Maltese club Birkirkara 5-3 on penalties after losing the second leg 1-0 to leave the tie locked at 1-1.
James Tomkins was sent off for retaliating to a Nikola Vukanac push in the 45th minute, marking West Ham's second red card in two European away games this season.
Bilic said his team had a lot to learn before their third qualifying round meeting with Astra Giurgiu.
"That two rounds, two stupid red cards, first in Andorra and now here," the Croatian said.
"We didn't get used to playing in Europe in this kind of atmosphere. We have to adjust, because we cannot react like that to provocation.
"It will happen again, 100 per cent. Both of them were a little bit hard for me but we gave them a chance to give us to give red card.
"After that, it was much harder for us. We were the better team at [the] end of the game, but we didn't create a lot and we didn't penetrate enough."
Bilic lauded his team for their character and determination despite the unconvincing nature of their progression.
The 46-year-old, who praised his penalty takers, said West Ham were unable to create as many chances as he would have liked.
"The most important thing is that we are through," Bilic said.
"They started better, they pressed up front, they definitely knew they would get used to conditions in this heat, they started better.
"We took the control of the game, but we didn't create chances, even though we we were around the box a lot and passing the ball.
"We lacked either the determination or quality to go into the box and create clear-cut chances."
