But the Hull lightweight quickly realised wife Lynsey and kids Leo and Lincoln are providing the fuel his needs to avenge his defeat to Yvan Mendy.
Cool Hand Luke will take on the Frenchman, who beat him in 2015, in an eliminator for four-weight world champ Mikey Garcia's WBC title.
And despite the first signs of the dreary British winter creeping into the air at his new Wandsworth Town HQ, he knows he is exactly where he needs to be to turn up the heat on Mendy.
On his move, Campbell, 30, told SunSport: "I’ve not regretted it, I love Miami, made some awesome friends out there who I'm keeping in contact with.
"But I know this is the place I need to be to get the best out of me so it doesn’t matter if the sun shines or it’s raining I know that being in this place, in this gym, is right.
"At first I felt a little bit guilty about spending time with my family on the weekends while I’m in training camp.
"But a flower doesn’t grow without water and they're mine. They are my fuel, why I make all these sacrifices, why I do what I do.
"Now I enjoy my family time at home and relaxing at the weekends when I’ve been away all week working hard.
"I don't feel guilty about it any more, I did at first but now I know this is what fuels me to do what I do."
Cambell has revealed he went into his first clash with Mendy completely unprepared for a tough opponent, who claims he is due a title shot after a seven-fight win streak.
And the gold medallist at London 2012 wishes he had linked up with 30-year-old McGuigan – who trains George Groves and Josh Taylor among others – earlier.
On his 2015 defeat to Mendy, he admitted: "I didn’t have a team – I was going in there blind.
"I feel like this is the first time in my pro career I’ve finally got a team around me, a professional team. I’m excited.
"Nobody’s even seen the surface of what I’m capable of doing and I believe that in myself my ability. I believe Shane will really bring that out in me – you’ll see the best of me and this is just the start.
"He’s tweaking things in my style, getting more out of my attributes working to my strengths and attributes as a fighter more as well as working on the weaknesses.
"He pushes me smarter, he knows when to push me and when to bring me back and that’s a very unique tool. I wish I had come here at the start of my career.
"I’ve done it so many times where a coach will work you too hard and not have any idea in his mind 'oh his power’s down, he looks fatigued, he looks like he’s slowing down' and they’ll continue to graft you hard.
"But it’s different with Shane, he knows how to bring you back to get more out of you.
"I’ve never worked so hard, the training regime we’ve got going on here at the gym it’s tough, it’s physical and it’s hard.
"He's got two tall southpaws with me and Josh and he trains us both differently, we've got healthy competition – you can work against each other and push forward."
Looking ahead, Campbell has one eye on Linares, who inflicted his only other career defeat after a split decision against in a WBA title match last year.
But in truth there is only one thing on his mind, following former Team GB team-mate Anthony Joshua – who headlines the show against Alexander Povetkin – into the ranks of world champions.
He added: "There’s some mega fights for me, I’d love to clean my record.
"I’ve got to take care of business on the 22nd. I'm looking for an impressive win – either by points or by knockout, it's got to be impressive.
"Beat Mendy, then I’d love the rematch with Linares and then I’m back to undefeated ways.
"Obviously my main focus in all of it is to be a world champion, I really want a belt, I thought I was a little bit unlucky the first time around.
"But I really want to win a first title, defend it and be a solid world champion – a well-known world champion."
Victory on Saturday night will leave Campbell's ultimate goal well within his grasp.
But first there is the small matter of beating a man they call The Lion in front of 90,000 fans at Wembley.
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