Cleverly, 29, will face Braehmer for the WBA regular light-heavyweight belt in Germany on 1 October.
The Welshman's three career defeats have all come in his last six bouts.
"This is a must-win for me - I'm confident I can upset the champion," said Cleverly. "I believe this is my opportunity to turn things around."
Cleverly and Braehmer were due to meet in 2011 before an eye injury forced Braehmer to withdraw.
The German will be aiming for a seventh successful defence of his title, while Cleverly lost his WBO crown in 2013 when he was stopped by Sergey Kovalev.
Asked if this would be his last world title fight if he lost to Braehmer, Cleverly told BBC Radio Wales Sport: "Possibly so and probably so.
"I knew the world title opportunity would come back around.
"Sometimes you hit those plateaus - you peak and then have a bit of a flat period. But I think I've got through that and the best is yet to come."
The WBA super world light-heavyweight title - the body's top honour in this weight division - is held by Kovalev.
Cleverly's last fight was a points defeat by Andrej Fonfara in Chicago in October 2015, though he was encouraged by his performance.
"We [Cleverly and Braehmer] were meant to fight three times in the past but he never fancied the challenge when I was at the peak of my game and had a lot of hunger and fire," he added.
"Maybe he's taken the fight now thinking I've had a quiet couple of years and gone off the boil.
"Maybe he's thinking this is his opportunity to beat me but, as I showed in my last fight, the fire is coming back.
"I'm looking to become a two-time champion and I'm going to grab it with both hands.
"It's notoriously difficult for boxers in Germany against the home fighters, but I'm confident that I'm not just going to win, I'm going to win emphatically and take it out of everyone's hands."

Mary Burrows, who was chief executive of Betsi Cadwaladr health board, moved from Colwyn Bay, Conwy county, to London two months ago.
She is staying with her son while she receives treatment for breast cancer.
"Treatments that have not been approved by Nice are not routinely available in Wales," a health board statement said.
A £200m-a-year cancer drug fund was set up in England in 2011. There is no similar fund in Wales.
Mrs Burrows said her consultant in Wales advised her to go to the Royal Marsden Hospital, Surrey, for the next stage of her treatment because the drug she needed was not available in Wales.
She called the situation "distressing," adding: "A lot of people can't just move their family to another UK nation. There needs to be a debate across all of the UK about how we fund these treatments.
"Not just cancer treatments; advanced technologies and surgeries coming through that people will want to access."
Mrs Burrows left her role with the health board last January.
She said she had "arguments with myself" about the fairness of the Welsh government policy and if having a cancer drug fund takes resources from people with other illnesses.
Mrs Burrows' husband died two years ago of advanced melanoma after he was also unable to get treatment in Wales, she said.
Now she is calling for more investment in the NHS "across the board".
A Betsi Cadwaladr spokeswoman said: "Where a clinician wishes to use a treatment that has not received Nice approval, they can make an application to the health board under the all-Wales individual  patient funding request process.
"These requests are con­sidered by an expert panel. Because each patient is different, each case has to be individu­ally assessed."
Welsh former world champion Nathan Cleverly believes his world title fight against Juergen Braehmer can be a turning point in his career.
[NEXT_CONCEPT]
A former head of a Welsh health board has moved to England in order to get a cancer drug.