Swans jumped to a 2-0 lead for the visitors fought back, with Aguero scoring a controversial winner.
Following the dramatic late victory, Bernardo spoke of the incredible come-back, which left City still in contention to achieve an unprecedented quadruple of the Premier League, Champions League, FA Cup and the already secured Carabao Cup.
"After the first goal I think we were perfect. The way we pressed, the way we were with the ball, very aggressive," said the Portuguese midfielder.
"We're very happy with the win. All four competitions, one of them is done, we won. Into the next three."
Asked if he thought the quadruple was possible for City to achieve this season, Aguero added: "Always possible, always.
"Sometimes these comebacks happen, it is important that we've qualified for the semi-finals, so we're happy.
"We always believed it would come, always we fight."