I mostly said that because I'm annoyed by the arguments constantly made by many people about "freedom" or "controlling your own body." So, I guess I'm not really saying that people shouldn't own their own bodies, but I will go on the record as saying that I think just because something is rightfully yours doesn't mean you shouldn't be restricted from doing things with it just because it doesn't directly harm others. Suicide is one thing that indirectly harms others through emotional pain or worse.
I agree that suicide can be selfish and cause emotional pain to others. But, the government shouldn't be regulating people's actions in order to prevent others from experiencing emotional pain. I can't think of a single example of a law that does that.
"Society" is not an entity in itself, it's simply the sum total of individuals and institutions. There is no "common good", just the good of different groups and sets of individuals and institutions. By restricting individual rights to benefit the "common good", you aren't benefitting "society", you're just benefitting some individuals and/or institutions at the expense of a smaller number of individuals and institutions.