Boro took three points from a possible 15 before ending their five game winless run with successive victories against Cardiff and Fulham last week.
"After MK Dons and Leeds when we were in a really bad run, it was really calm because the team had played really well," Karanka told BBC Tees.
"Playing in that way, with this squad, I knew that it was going to be time."
Before suffering back-to-back Championship defeats by Bristol City and Nottingham Forest in January, Karanka's side had lost just four league matches in 2015-16.
However, the Boro boss insisted two wins in four days to move to within a point of top spot had restored confidence at the Riverside Stadium.
"The time arrived against Cardiff. The main thing was to win," Karanka said.
"Now the team is more confident again - the team feels that they can win every single game. So for that reason I am confident for the future."
Middlesbrough are third in the Championship, equal on points with Hull City in the second automatic promotion place, with at least one game in hand over both sides above them.
They next face Blackburn Rovers on Tuesday.
Middlesbrough manager Aitor Karanka says he knew it would just take time for his side to recover their form.