Yeah, I think it could be different things... for me, maybe self-esteem and self-protection (like Goingtogetthere mentioned). If T (or anyone!) abandons me - that's rejection. That makes me feel pretty awful - like I'm not a worthwhile human and like no one will ever love me or care about me (yikes!!!). But if I walk out first, that doesn't apply. I might feel a little wimpy for walking out, but... it's still better than the awfulness.

I'm wondering too if it's something to do with "control". Feeling like you're on the brink of being abandonned means you don't have control - something external may or may not happen that would upset your equilibrium. By walking out, you get to be in control. That can feel better...