Madrid were beaten 2-0 by Celta on Sunday to end their hopes of winning the title as Atletico Madrid and Barcelona will now decide among themselves who will be crowned Spanish champions in next week's match at Camp Nou.
"After a great season in this competition the team wasn't up to scratch and we've let La Liga slip away from us in a very bad way," Ramos told the official Madrid website.
"You go home feeling sad and disappointed for having let this unique opportunity to win the title pass us by. We have given our all on the field and tried to play as well as possible. We shouldn't take anything away from this league season."
The defender then went on to stress that Madrid must now turn their attention to this month's Champions League final against Atletico.
"We can't complain or let our heads go down. We have to switch gears from the last few matches.
"Now it's time to think about the Champions League final and be self-critical. That's football: one day you're up, the next your down. Madrid are capable of anything. We have to reflect and draw conclusions."
The Champions League final takes place in Lisbon on May 24.