The 29-year-old has endured a horrific personal summer after losing his father to cancer before one of his cousins was electrocuted in a swimming pool.
Defoe, who has been named in the squad for England's upcoming World Cup qualifiers with Moldova and Ukraine, admits that he has a different outlook on life following his losses.
"You get disappointments in life and then everything turns good but it has been difficult for me and my family. It has been hard, especially with my dad," said Defoe. "From day one, when he was diagnosed, I was with him from the first meeting in the hospital. I am only 29 and to deal with that was quite difficult. I had to tell dad my 'it will be okay and be positive, keep praying and have faith.'
"It makes you think about your life and what is important. I have got a big family and we have always been close. If you have an argument with someone and you sulk, sometimes you don't want to speak to them. But it is important to keep your friends close to you and do the right things. It did make me think about my life especially with what happened with my cousin as well, electrocuted in a pool. She was only 21.
"To be honest, the only time I am really at peace is when I am training and playing. Obviously when you are on your own you start thinking [about] stuff."
Defoe could earn his 50th England cap against Moldova on Friday.