I have a trauma-based personality disorder, which sometimes manifests itself in episodes of often uncontrollable bouts of verbal violence. I prefer to direct this to people on the internet (as opposed to actual people), as I don't wish to be violent towards people I actually care about.
Because it's often real fucking scary? My every past (often futile and misguided) attempt at forming a (stricly monogamous cishet) relationship ended for one reason (me) or another (the other half). I have been hurt by myself and others, by my own feelings or the other's or the lack thereof from either. Now I live together with an incredible woman who gets me and I get her and our futures have so far seemed well aligned and stuff and I never have to fear to be judged or ridiculed by her unlike in previous attemps and I know she trusts me (and I trust her when she says so) as well. And yet still I find myself fearing: what if she'll just stop loving me because of xyz? Because everyone else has left so far (sure I might have personally driven away a few because of my fears and insecurities, and maladaptations or other toxicities, but I've grown from those times emotionally). It's real scary to open your shell and be at your most vunerable, but it is also required. Not everyone can be expected at any point to be able to do it just like that.
That's my two cents.