The Camp Nou club, who take on Cartagena in the last 32 of the Copa del Rey on Friday, suffered a 2-1 UEFA Champions League loss to Ajax a just over a week ago before falling to their first league defeat of the season against Athletic Bilbao on Sunday as they went down 1-0 at San Mames.
And coach Martino has conceded the buck should stop with him.
"When we lose, that is my responsibility," he said. "It worried me that we weren't able to react after Athletic's goal.
"At the end of the game, the team shouldn't get restless and stick more to our game, no matter the score.
"The mood suffers when you lose two games and this game (against Cartagena) can help us.
"Pessimism around the team? There are two options - it can hurt us, or it can make us stronger."
The coach did offer some hope to Barca fans, with the news that Lionel Messi's recovery from a hamstring injury is progressing as expected.
And the Argentinian also refused to rule out strengthening his squad in the January transfer window.
"Messi's recovery goes as planned," he continued. "We hope that he will be back at the start of the new year.
"I didn't yet decide if we will sign someone in the winter transfer window. There's time left to make a decision."
