Halford joined Sean O'Driscoll's side last week but waived a pay-off for the remainder of his contract, thought to be around £1.5million.
Pompey administrator Trevor Birch has spoken of his frustration at other players stalling on negotiations but the 27-year-old insisted he was more than willing to help.
"If you speak to people close to me they will say I am not a selfish person - and I always wanted the best for the club," Halford told The Portsmouth News.
"It was not a hard decision, to be honest. I wanted to do whatever I could to help Pompey and the fans. It had to be done and I was willing to walk away from my future earnings.
"Obviously each player is a little different in all this and I have long been prepared to walk away from future earnings and the contract I was on."
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