Petrov "thought leukaemia was just a cold"
Petrov found out about the severity of his disease after he developed a fever following a Premier League match against Arsenal.
"At the start I thought it was just a cold, nothing serious but just something normal," the Bulgarian midfielder told the Villa website on Wednesday.
"I can say I'm lucky because some people with this disease will die very quickly and I managed to keep battling and still be here, still standing.
"It's a great relief. You can try to explain to people but they probably won't understand. Only people who have been through it and the closest people will know what you've been through."
Petrov, who has received enormous support from Villa and his old club Celtic as well as from other Premier League clubs, said the more high intensity treatment was now over.
"It was a very, very long year but now, after all this treatment, I can go back to a normal life," said the 33-year-old who must keep taking tablets for two years.
"I can start doing things that I couldn't do in the last year. I can take the kids to school, I can come here, I can start doing a bit of work and losing a little bit of weight."
Petrov has been to Villa Park on numerous occasions this season, receiving a minute's applause in the 19th minute. His old shirt number was 19.
He plans to attend every game until the end of the season as Villa, fourth-bottom of the table and three points above Wigan Athletic who have two games in hand, prepare for a relegation scrap.
"I think it's about belief. Villa are in a position at the moment where people say we are fighting relegation. We are, but so what?," said Petrov.
"You need to believe that you are going to be out of that situation."
Petrov said he was looking forward to spending more time with his family before starting a new career raising awareness about his debilitating illness.
"I'm hoping to open my foundation soon and I'm going to start raising money and awareness for leukaemia and different charities and I'm in the process of doing this at the moment," he said.