One step forward, two steps back

What's on my mind this morning is how can I learn to develop deep trust and intimacy with another person when I know they are capable of hurting or leaving me at any time? How do you develop these things without deluding yourself to some extent? Without deciding that you can predict what someone will do in the future? Maybe it's not self-delusion, but rather acceptance of risk? But that's a terrifying prospect. To accept the risk that you might make yourself vulnerable and then get deeply hurt, that you must truly give without expectation. To expect is to think you have some influence over what someone else will do in the future. We're taught to expect in return. We're not taught to give without attachment to the result. I don't know if I know how. Intellectually I understand, but my body is resisting with feelings of fear and anxiety.