The La Liga champions suffered back-to-back defeats for the first time since January as a Dele Alli brace and Christian Eriksen strike saw Spurs to their win at Wembley on Wednesday.
But Ramos insists Zinedine Zidane's side, who are second in Group H, will bounce back.
"We understand that the fans could get disillusioned after recent results, but Real Madrid always fight back and if anyone thinks that we're done for, we'll put them in their place," the Spain defender told reporters.
"From my experience at Real Madrid, when you lose a couple of games, people begin to talk about a crisis. You have to stay calm and be united.
"We're alive in our favourite competition, the Champions League. We must stay calm, remain united and convinced that the Real Madrid we know will be back very soon."
Pressure is growing on Madrid after recent games and their chances of getting a result against Spurs were over when Eriksen made it 3-0 in the 65th minute.
Ramos felt the result was harsh on his team, who host Las Palmas in LaLiga on Sunday.
"The score line is a bit deceptive, not to take anything away from Tottenham," he said.
"They played very well, they're a great side, with a great stadium and fans who really make a difference.
"We've benefitted from Borussia Dortmund's draw [against APOEL] and we're still well in the mix.
"We would have liked the result to be different, and to be fighting to be top of the group. We did certain things quite well but that's overshadowed by the result."