He admitted he has been going through a tough time recently but remains confident he will rediscover his top form.
"It is not the first nor the second time I have encountered a complicated spell," said the 25-year-old Spain international, who has not scored for Barca since February.
"I play with a smile on my face and I still believe in my ability.
"For me it is more important that the team wins than what people say about me.
"I'd be worried if I had chances to score. Scoring is crucial in football, but I have other important tasks on the field."