You look into his/her eyes and you tell him/her that. It's the same warning you've given a hundred times. A thousand times. You've been right every. single. fucking. time. Being right is starting not to matter one. fucking. bit.
This is how it goes:
You smile at each other, eyelids getting heavy. Happy. It's more than a date, less than a relationship. It's not an interview, but not...not an interview. It's not daring to say it, but looking ahead and imagining your future with him/her. Your house. Your kids. Your in-laws. Your finances. Your pets. Your fights. Your compromises. Your secrets. His/her secrets. It all seems...good. You look into the eyes that are staring back at you. What is that look? What does that mean?
Your eyes open up wide again. Then, unfortunately, yet, predictably, you open your mouth. You start talking.
"This won't end well, you know, you see... everything you see about me that you think you like you will stop liking, everything you think is charming you will hate me for, everything adorable becomes painstaking wretched, you see, I can't do this, I am bad at this and it has never worked before and it will never work, everything I give to you I am taking away from me and I have so very little to start with that I can give nothing, not my time, not my space, not to mention I am a freak, I can't get close to people, I scare easily, I startle easily, I don't sleep, I disappear for weeks on end, I don't return phone calls, I cancel plans, I get scared to leave my house, I want to go away on vacations, but I want to go alone, I don't want to talk about my family, all I want to do is talk about work, because it's the only thing I am good at, and I am actually not that good at it, I am just good at faking it, and right now you're going to say it's all fine and that you like your space, too, and you hate those couples who have to be around each other all the time and it's awesome that I'm not like everyone else and if I were like everyone else you wouldn't be interested in me, and you don't like to talk on the phone anyway, and we can do this if I can just have a little faith in you, and I will have a little faith in you, but then in a week, two weeks, three weeks, what I have won't be enough, who I am won't "work for you" and yes although it's true I had given you that warning in advance doesn't mean you have to like it, and you will tell me that every chance you get, and then I stop calling, then you stop calling, then, you move on, I move on, or the other way around, and I am back to where I've started, and you are back to where you've started. So, you see? This won't end well."
He/she looks right back at you. A bemused half-smile on his/her face. Is it confidence? Is it an act? You have no fucking idea. He/she asks "And how many times have you given that little speech?" A lot, you admit. More times than you care to count. But now you've said it. You're now off the hook. You can now continue sabotaging your own life and your own happiness, and now it's all on him/her when this whole thing goes so horribly awry, which it is absolutely going to do.
You can't stop yourself. You're on a roll. You must continue. You tell him/her every bad thing about you. Just so there are no surprises down the road. You fail to disclose even one good thing about you, as if there is nothing ever good to tell. You never say how loyal you are. You never say how you look good in a gown. You never say how hard and often you will make him/her laugh. No. What you say is "this won't end well."
Maybe there's room for change. Maybe next time, you can shorten the speech, or what the fuck? Eliminate it completely. Because what if you're wrong? What if... it could end well?
What if you learned to just shut the fuck up?
Next time, maybe you should try it. Next time, maybe you will.