The 23-year-old star quit the chart-topping boyband in March 2015 and has subsequently adopted a more mature sound with the launch of his debut album 'Pillowtalk'.
In an excerpt from his eponymous autobiography, he said: ''Every lyric I've ever written has a story behind it. All the hard work that went into the creation of 'Pillowtalk' was worthwhile because, as soon as it was finished, I intuitively felt I was on the right path.
''It was a sick cut, nailing the exact sound I wanted to capture in my music. I was also able to sing about a subject that I hadn't really been able to go near while I was in One Direction: sex.''
Zayn also revealed he hopes his autobiography will help to clarify some of the misconceptions that surround him.
He said: ''I'm going to show you as much as I can so that you can judge me on my own terms, not on what the press or anyone else says.''
In recent months, Zayn has cancelled a number of scheduled appearances because he was suffering from anxiety.
In June, for instance, Zayn was due to perform his first UK gig since leaving One Direction at the Capital FM Summertime Ball in London but pulled out at the last minute.
He said at the time: ''I flew into the UK last night to appear in my home country in front of my family, friends, and most importantly my UK fans.
''Unfortunately my anxiety that has haunted me throughout the last few months around live performances has gotten the better of me... with the magnitude of the event I have suffered the worst anxiety of my career. I cannot apologise enough but I want to be honest with everyone who has patiently waited to see me, I promise I will do my best to make this up to everybody I've let down today
''I know those who suffer anxiety will understand and I hope those who don't can empathises with my situation.''
More recently, he pulled out of a planned appearance at the Autism Rocks Arena in Dubai on October 7, saying he didn't feel ''sufficiently confident'' to take to the stage.
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