Lubbers said his fight with former world champion Muhammad Ali, for which he earned $125,000, made him mentally stronger.
The 73-year-old and his partner Ria have been living in poverty in southeastern Bulgaria for the last two months, only to receive help after his story grabbed huge attention in the Netherlands following a TV documentary shown last Sunday.
They survived the freezing conditions in a broken-down van, lacking electricity, water and sanitary facilities, Looking after stray dogs.
Ria’s health deteriorated suddenly and she was rushed to hospital on Friday in critical condition.
Lubbers said her condition had improved slightly but she would remain in hospital for a few more days at least.
“The most important (thing) now is that my girlfriend returns in good condition and can see the dogs again," Lubbers told Reuters just outside the dilapidated van in the countryside near the village of Kosharitsa.
"In Bulgaria it's impossible to live in a house with so many dogs. It's possible if you have three or four dogs but at one moment I had 16 dogs with babies.
"I would live a normal life but I don't know if I can live in a house. I'm more like a camper."
Lubbers, who represented the Netherlands at the 1964 and 1968 Olympic Games before turning professional in 1970, said his fight with former world champion Ali, for which he earned $125,000, made him mentally stronger.
"I've learned from the fight, so I could survive here," he said, adding that he and Ria had received food and clothes from local people as well as Bulgarian mastika (strong anise-flavoured drink) to keep them warm in the freeze.
Many in the Netherlands were shocked to see their boxing hero in such a desperate situation and more than 12,500 euros was collected after a crowd-funding campaign was launched.
Rudi's son Marco, who hasn't been in touch with his dad for two years, arrived in Bulgaria after watching the documentary while Dutch people, living in the Balkan country, arranged a temporary shelter for the dogs.
Lubbers worked at funfairs with Ria for several years after retiring but became homeless after she was declared bankrupt in 1999 and they lived in Lebanon, Morocco, Egypt, United Arab Emirates and Portugal before arriving in Bulgaria a few years ago.
Lubbers said he had remained friends with Ali who fought him in 1973 as he prepared for a rematch with his great rival Joe Frazier.
"Years after the fight, he (Ali) came to Holland," said Lubbers who revealed that Ali had told him something he would remember forever.
"Ali told me: `Rudi, you're the only white man from whom I ever learned something'."
Lubbers, never beaten by a Dutch opponent during his career, said he still watched boxing but was disappointed by modern techniques.
"I love boxing but boxing has changed," said Lubbers, who has suffered from asthma all his life. "It's more fighting now."