The Portuguese ace is aware of Real Madrid's renewed interest, but insists he only wants to play for United.
Ronaldo told The Sun: "I just don't care what the whole world seems to want to say about me or speculate about my future.
"I get angry but I'm trying to accept it's a waste of energy to be furious because it is not worth it. It's not by chance I've ended up at United. I always showed that I had the basic talent and commitment to become a professional player.
"Then my development here has been aided by the support and the correct environment for my talent to develop. There is an attitude of hard work here that I need and like. This season is massively demanding on all fronts, personally, for United and for Portugal.
"So what I'm trying to do is set everything else aside and be ready to give my utmost in every match from now until the end of United's season and then into the European Championships with Portugal.
"If I'm performing at the best level of my life, then it's not by fluke. Far from it - I've worked damn hard to try and achieve exactly that.
"I'm pushing myself mentally and physically. I'm working constantly to better myself - it's for those reasons alone, and not by luck, that the results are coming and the goals are flowing."
