These kinds of investments lead to a safe relationship with safe boundaries. And that's the kind of relationship were safe sex can flourish. The key to emotionally safe sex is boundaries. It is a paradox, of course, that healthy boundaries are what make possible the transcendance of boundaries that is part of sexual experience. But that's the deal.
Poor boundaries lead to unsafe and unsatisfying sex.
The first kind of boundary that makes for safe sex is a boundary around the sexual relationship. I'm not suggesting, of course, that monogamy is a guarantee for safe sex. But monogamy at least creates the structure within which safety is possible. Take just the matter of performance orientation. If you leanred about sexuality from the media you probably got the impression that any two people can have sex with accompanying vioins and fuzzy camera focus.