Debates on precedent autonomy and some forms of paternalistic interventions, which are related to questions of personal identity, are analyzed. The discussion is based on the distinction between personal identity as persistence and as biographical identity. It first is shown that categorical objections to advance directives and "Ulysses contracts" are based on false assumptions about personal identity that conflate persistence and biographical identity. Therefore, advance directives and "Ulysses contracts" are ethically acceptable tools for prolonging one's autonomy. The notions of personality and biographical identity are used to analyze the ethically relevant features. Thereby, it is shown that these concepts are operative in and useful for thinking in biomedical ethics. The overall conclusion is that categorical arguments against precedent autonomy or "Ulysses contracts" are based on misleading theories of personal identity and that advance directives are an ethically respectable tool for prolonging individuals' autonomy in cases of dementia and mental illness.