The 35-year-old singer and the Formula 1 driver called time on their five-year on/off relationship because of their hectic work schedules, and Lewis admits his world has been ''turned upside down'' and he is finding it hard to stay positive.
The 28-year-old star told Sky Sports: ''You have different people who are able to keep in their emotions - I have a Finnish trainer, for example, who doesn't show any emotion and they are always able to control it.
''Me, I wear my heart on my sleeve and that gets me in trouble a lot of the time and I generally find it very, very hard to fight my emotions.
''I'm going through... I'm trying my hardest to be positive but I'm going through a really, really tough time at the moment with the loss of someone really, really special in my life.
''My world's turned upside down, but I have a job.''
He added: ''So I'm really trying to pull myself together and keep my head up, but it's so hard to do.''
'X Factor' judge Nicole revealed earlier this week that she is also struggling to cope with their split and said it ''really sucks''.
News of Nicole and Lewis' split materialised earlier this week, but insiders say the pair broke up around one month ago.
The sports star recently hinted that he was planning to propose to the brunette beauty for their sixth anniversary.
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