Blatter, president since 1998, will step down in February amid an inquiry into allegations of systematic bribery.
The 79-year-old was elected for a fifth term in May but then stood down.
"I did it because I wanted to protect Fifa. I can protect myself. I am strong enough," he said.
"I know what I have done, what I have not done, I have my conscience and I know I'm an honest man. I am clean. I am not a worried man."
Two criminal investigations into corruption at Fifa are continuing, after seven top officials were arrested at a dramatic Fifa congress in Zurich last May.
That includes an inquiry into bids for the 2018 and 2022 World Cups, leading to speculation that Russia and Qatar could be stripped of football's flagship event and a re-vote ordered.
But Blatter said: "The institution is not corrupt, there is no corruption in football, there is corruption with individuals. It is the people.
In an exclusive interview with the BBC's Richard Conway, Blatter also said:
- He was not "morally responsible" for the likes of former Fifa executive Chuck Blazer, who admitted he accepted bribes in connection with South Africa as 2010 World Cup hosts.
- The 2010 World Cup was "the cleanest World Cup that had have ever been done".
- "Fifa was the suffering party" but it would emerge positively after the "tsunami" of allegations that had hit it.
- He recognised "there were a lot of fans using the [media] devices and social media where they said 'kill Blatter'"
- But he said there were different opinions in Asia and Africa, adding: "I'm at least respected because I and Fifa have done a lot".
- Source: BBC