Even slaves had the ability to harm themselves and kill themselves. Roman law said someone selling a slave had to disclose that the slave had attempted suicide. Yazidi sex slaves are committing suicide at a high rate.
As to the freedom to harm themselves through bad choices, carelessness and deliberate attacks on someone regardless of the odds you will get hurt have always existed.
Let's say you're discussing the ability to make a choice like smoking cigarettes, a free love attitude where you don't care about sexually transmitted diseases or eating bad foods. You will get to live with the consequences, and society's solution is easily letting them live with the consequences. Society then doesn't spend a lot of money treating someone suffering by their own mistakes, like telling smokers we'll give you an oxygen tank but not a lung transplant, the obese person doesn't get extra privileges because they are fat, the person with HIV and AIDS gets pallative care and not 100,000 a year drugs.