The Portuguese winger underwent ankle surgery after Euro 2008 and has been forced to miss the start of the Premier League season.
He admits it has been a difficult time but believes he is now making good progress and should be back soon.
Sir Alex Ferguson does not expect Ronaldo to be available again until the start of October but the 23-year-old was pictured jogging round United's Carrington training base last week after being given the green light to step up his rehabilitation.
"I have never experienced a situation like this, being two months without kicking a ball. I just want to be fully recovered," Ronaldo told SIC.
"I am not used to being sidelined. I feel sad, but the worst moment has already gone and I recognise that I must patient.
"I feel well, and the time of kicking a ball is coming. Playing football - this is what makes me happy."
Ronaldo is a leading contender to win the Fifa World Player of the Year award after inspiring United to a domestic and European double last season.
He is proud of his achievements over the past 12 months and feels he has a good chance of scooping the prize.
"I think that I had very positive campaign last season," said Ronaldo.
"It would be a dream that becomes reality to win it. Not any player has done what I did last season.
"I believe I can win it this year."