Now that I've been in middle age for the past 3 or so years, I'm pretty sure that my loyalty in the years left to me must be to my body.
In the past? I was primarily all a-flutter about whatever my flighty Head told me, with my figurative Heart chiming in occasionally. As in (head), "This person is so creative and original, so different! I LOVE her!" and (heart, overriding head) "Well, this person is absolutely shitty to ME personally, but look... She once collected money for a friend's abortion! She once comforted a gay boy whose high school friends and parents were being unappreciative of his soul! She once cried upon learning that her sister's GoodWill coworkers were mean to her! What a great person! I LOVE her!"
When I say loyalty to my body, I mean it literally. An example: My very first lover back in '87 gave me a sexually transmitted disease. And then DENIED that she had given it to me! I'd never had sex before, and she'd had sex with probably 300 people; but she would never admit that she had given me the STD. We were together for over 2 years, and I brought it up maybe twice during that time... she would never admit it. Hey, as a virgin, I had a RIGHT to be pissed off about getting an STD on my first outing! Jesus. The vast majority of newbies get SOME sort of "fun trial period," don't they?? And, more importantly, the fact that even after we became more intimate over time, she never admitted that I now had an STD solely because of her. (If both parties had been sexually active for years, there's of course a gray area... In our case, though... Nah.)
That hard-core STD fact, and her psychological game-playing, probably kept me with her much longer than necessary -- "Who will want me now?" and all that. My head and my heart initially liking her, being fascinated, wanting to discover more, but my BODY, the realist, being utterly repulsed.
Being true to my body also involves paying attention to its responses. Who floods it with feel-good endorphins? Who makes it tense up? The girl I was in love with my senior year of high school, for instance... One Sunday, I was in my bedroom wracked with cramps to the point of throwing up from the pain. Ginny showed up at my house unexpectedly --- when she walked into my room, what I now know were endorphins kicked in; the pain immediately disappeared.
Conversely, with my first lover Mollie, the STD expert, I was almost immediately, constantly paranoid. Same paranoia with Sandra, much later, 2008, via the Internet and then once we met in person. With the one male lover that I've had, in the 1990s, there was no paranoia at all. He was married, which created a barrier that made me MENTALLY angry, but there wasn't any sort of "neurological" repulsion that made me immediately tense up around him.
Gotta start paying attention to that sort of pure bodily reaction. The inexplicable. The key to an innate sort of physical/chemical happiness that leads to longer-term emotional/mental ties. Going purely mentally on and on and on with those who simply don't make me feel good has been ridiculous.