The veteran defender claims his side were expected to win 3-0, but highlighted the difficultly of beating Bayern Munich in the Champions League.
Marcelo and Marco Asensio cancelled out Joshua Kimmich's opener to lead Madrid to crucial victory against the German champions, and the defender knows the second leg will not be any easier for his side.
Bayern controlled possession and were unfortunate to surrender two priceless away goals to the two-time reigning champions heading back to the Santiago Bernabeu.
Speaking afterwards, Ramos revelled in the triumph, though the centre-back quickly turned his attention to the return fixture in the Spanish capital."We were expected to win 3-0 but it was always going to be difficult," Ramos said. "This is what the Champions League is like and we enjoyed being involved in a great game. The team put in a solid display, defended well and we were aware that it wouldn't be easy.
"It's really tough to come and play here against great opposition and fans worthy of the Champions League. We now have to finish the job off at the Bernabeu. We haven't achieved anything yet and have to keep cool and show Bayern respect."
Ramos added: "Given the circumstances, when you take the lead you naturally end up dropping deeper and you suffer a bit. When the scores were level, Bayern really went for it and we were able to hit them on the counter.
"It's important that whoever plays offers that spark, keeps the performance levels up so that we all end up winning."
Madrid held the same lead against Bayern in last year's Champions League quarter-finals and were pushed to extra time at the Bernabeu before eventually winning out.