And the 29-year-old has enlisted the help of former WBU welterweight champion Michael Jennings as he bids to claim the EBF light welterweight title belt on December 4.
McDermott, of Higher Road, Longridge, is scheduled to take on Warren Harrison, who defeated him with a fifth round knockout last month at Rumes nightclub in Preston.
But McDermott says it will be different this time as he is being trained by a world champion.
He said: "I have spoken to Michael after each of my fights and he has told me that my fitness let me down.
"So he has decided to help me and I will be going to the Collyhurst Gym in Manchester to work with him.
"I have been getting medicine balls thrown at my stomach which hurts but it is meant to make me better prepared for body shots.
"We have been training for the past eight weeks ever since I knew it was being re-scheduled.
"I am taking this seriously as every time I have a day off you will see me in the gym whereas in the past I would have been relaxing."
McDermott believes that team Jennings will put him in the box seat ahead of the fight.
Michael Jennings has been working as McDermott's fitness coach while Michael's dad Ray has completed a dossier on his opponent.
Terry added: "I am really happy to have them helping me as we have a game plan worked out and I will be listening to what Ray is saying.
"He has been studying Harrison and I think they can help me get a win.
"My coaches have been great and now I think it is time that I repaid them."
Tickets for the fight are priced at £25. Anyone interested in buying tickets should contact Terry on 07932359830.