In the lead-up to London, Magnussen, the 'missile' of Australian swimming, had promised to win the 100 gold medal and the 4x100 freestyle relay. However, he was pipped for gold in the 100 while the relay team finished fourth.
Amid reports of bullying and disharmony during the campaign, Australian swimmers delivered their worst Olympic performance for 20 years, failing to win an individual title and ended up with one relay gold, six silver and three bronze medals.
"I think more than anything I got wrong (was) my life outside of the pool," Magnussen said in Perth on Wednesday.
"I did everything I needed to do in the lead-up in the pool. (But the results) just showed there were some imbalances."
Magnussen, who will be back in action this week when he hits the pool for the Aquatic Super Series in Perth, said London had taught him a lesson and he hoped to be a better swimmer by the time the next Games are held in Rio in 2016.
"I've made a lot of changes in my life and I'm feeling really positive about where I am at the moment. I'm in a good spot mentally," he said.
"I've taken on a mind coach - not necessarily purely for the psychological side of swimming, but for my life in general.
"I've really worked hard on trying to be a more positive and easygoing person. I think it's paid huge dividends both in and out of the pool.
"London was a great opportunity for me to learn what I did wrong. Hopefully that will provide me with a really strong base for the next four years going into Rio."
(Reporting by Sudipto Ganguly in Mumbai; Editing by Peter Rutherford)