The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
If it's a Power Incontinence sort of thing, that's It's Not You, It's Me
If the problem is specifically related to the logistics of intimacy, Man of Steel, Woman of Kleenex.
If they believe that life with them would make the other miserable, I Want My Beloved to Be Happy.
It's Not You, It's My Enemies would apply in situations where there's no specific enemy or the threats are more abstract, however- say, a person is a living Weirdness Magnet, and know that anyone who gets involved with them gets sucked into the constant danger and misadventures.
Edited by Scorpion451
Pushing someone away because you think you’re too dangerous to be around.
Not It's Not You, It's My Enemies.