The 25-year-old is loving football again following his Fratton Park switch at the turn of the year.
Harry Redknapp rescued Defoe from his Spurs misery and allowed him to flourish on the south coast.
The ex-West Ham striker has responded with 10 goals in 16 Blues games, including one against Everton on Saturday, to return to the England set-up.
He is now expected to line-up alongside Wayne Rooney against Andorra tomorrow as Fabio Capello's side kick off their World Cup qualification campaign.
And Defoe believes his Blues move has worked wonders.
He said: 'I have benefited from moving to Portsmouth and I am so glad I made that decision.
'I was at Spurs for three-and-a-half years and most of the time I was really happy. I had some great moments there.
'But towards the end, it started to get difficult.
'There comes a time when you need to move on, play football and be happy again. That is what happened to me.
'I think most people would describe themselves as confidence players.
'When you are playing well, you feel confident and believe you are going to do well in games. That is the kind of form you want to take into international matches.'
It's been almost two years to the day since Defoe bagged two goals in a European Championship qualifier against Andorra in a 5-0 triumph.
That is almost half of the five goals the Pompey striker has netted in his 29-game international career.
But he's hopeful of adding to that tally tomorrow.
He added: 'You have to believe you will get chances in games like this. It is down to us to take them.
'As a forward, it is a game you want to play in. But you also have to recognise it is a massive game in terms of qualification and a win is really all that matters, irrespective of the score.'
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The full article contains 364 words and appears in The News newspaper.