I would posit, for inspection... a relationship begins in hope and ends in fear. Experientially true for me, to date. A universal? Who knows.
I would presume that fear is not the only thing that ends a relationship. I can see a simple drifting apart as a possibility ... but I have not seen such. In my experience, someone always senses a drifting apart (whether it is there or not), and fear enters the equation.
What makes a relationship? (I ask to test whether it's fair to say fear can unmake it on its own... or whether it is more the drifting apart or even a simple "not being right for eachother" (not that that's anything near simple, likely, but ...))
Bouncing around in my head, in the order they come to MIND, but not in an order of importance: good sex, good kisses, good time spent together doing things together, good time spent together doing nothing, good time spent together doing separate things, and good time spent apart.
Is there anything more that is truly necessary for a relationship? Of course there are dreams -- there are two pasts that some people worry about (a truly silly enterprise, I think) and two futures that somehow need to be melded into one; it seems always easy to meld two presents into one -- that happens on its own, effortless.
I would say that there is nothing more truly necessary for a relationship. Or perhaps ... let me say ... other things that people would normally consider important I think of more as elements of the above. Interests do not have to be common to the two so long as they can integrate. Ideals do not have to be common to the two so long as they can integrate. Ideologies do not have to be common to the two so long as they can integrate.
It is a true requisite that the two must draw pleasure from and provide pleasure to eachother. Fear in its pure form is *not* pleasure. One can derive pleasure from fear, but that's not the subject of this. Here we talk of fear on its own.
In a split moment can come the fear of pain. Here we finally have laid enough ground perhaps to circle back to the quote at the top: "I'm very good at protecting myself." I think that fear itself, presuming two people are good to eachother, can destroy a relationship utterly. The fear of fear and ad infinitum... it's a dangerous curse, self-preservation. Or no, it's not even truly self-preservation -- pain is generally a measure of being in danger of something worse. Emotional pain is typically the worst that is going to happen -- if you can get past that, then you are better.
Do not fear pain. Only fear what pain implies.