At the launch of his new autobiography 'Faster Than Lightning' in London, the world's fastest man said: "If you want to be the best, or you want to strive for more, you've got to set goals in life."
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The major party leaders' campaigns for the General Election will remain suspended on Wednesday following the Manchester terror attack.
Thousands of people have donated to help the families of the victims - as well as a homeless man who came to their aid.
Some children, particularly those who have been more directly affected, may show symptoms of stress and trauma.