Newsbeat's been speaking to 22-year-old Josh Cook, a semi-professional rugby player from Huddersfield who says he should have the right to die when he chooses.
He's been diagnosed with Huntington's disease, which affects the nervous system and will eventually leave him severely disabled.
Josh says he's watched many of his family die slowly, in pain and doesn't want to end his life "stuck in a chair, unable to move apart from muscle spasms".
Last year the High Court ruled against allowing other severely disabled people from having assisted suicides.
The Court of Appeal has now backed that decision and rejected challenges from the family of late locked-in syndrome sufferer Tony Nicklinson and paralysed road accident victim Paul Lamb.
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