My opinions:
The first two instincts together create an overall "vibe" of what realm of life feels important. For instance, so + sx = camaraderie and intimacy. Lasting involvement with someone you felt some spark with. The first instinct will lead, but depending on the person the level by which it comes out ahead is different. It feels obvious that these areas of life should be related - to the point where it's not always intuitive which instinct is "being used."
Many ppl think intimacy = "caring friendship" - I have an sx/sp friend who doesn't "check in" on me, she frequently leaves abruptly in the middle of a text string and never comes back. Yet she loves me a lot. So whatever other expectations (or obligations) I felt towards our relationship, it's probably not sx.
Ppl can experience anxiety around the second instinct, and even the third (although it gets twisted b/c it feels...indirect, colored strongly by the first instinct.) But much of the time when experiencing 2nd instinct anxiety the first instinct anxiety is a little bit there too, etc. But the weaker instincts really can get shelved for a while.
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The Fauvres teach that you can be positively or negatively identified with an instinct, which feels simplistic, but it's true that not everyone "likes" their primary instinct. Plenty of people minimize the extent to which their first instinct rules them. They will say "Oh I don't care about dating much." "I'm not materialistic - money is not my value." This is also, I think, b/c you develop a certain amount of morals, and even ability to handle deprivation around your first; but the person who doesn't "care about dating much" is still putting a lot towards their partner once they are really in a good relationship. The non-materialistic person may not like extravagance but can still work hard to have something in excess of what they use - for a rainy day. Maybe it's a way of saying, "this isn't all that I am - this isn't everything on my mind." Once you start getting enough of the first you can begin to relax towards other things.
One of their interesting points is that you can be positively identified with your last instinct, thereby finding it easier to pick up.
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I am one of those who find my first instinct too stressful.
After studying instincts for a while I see the top instinct as a beginning point, too. It's an area of life you are anchored to no matter what, through which you might ease into the others. When I handle the first enough, it's time to get to enjoy the second, and so on. It's like everything unfolding now into the fullness of life.