There's actually a giant caveat in the whole "anchor collapse" thing. So big you could drive a ship through it.
It's really really easy to fail to get in touch with the entirety of the motivation behind one side - especially when it's a far mode thing.
If you're only commanding part of the emotional weight behind one side and the entirety of the other, then the latter side has an unfair advantage. It's like deciding where to eat with your new friends and saying "eh, I'd prefer not to eat there, but it's no big deal" when in reality you have a nut allergy and that place will kill you. The decision might go your way, but only if there happens not to be a strong opposing force. Probably best to speak up with your full source of motivations.
There are a bunch of reasons this can happen.
Perhaps we think that we "shouldn't" care about something that we care about - or are ashamed that we do. You can't force it one way or another. You can't force one anchor to weigh more heavily on your decision than the other - any more than you can make one object weigh more than another by pushing on the balance. You care about what you care about, and there's nothing "you" can do about it. (except examine whether your instrumental desires actually serve your more-terminal desires and hope they'll shift on their own before you collapse them)
But it can be hard to admit sometimes. So we want to force it one way or another. To fit in. So the full force of "unwanted" desire is not gonna be brought to the table until we feel strong enough to face this. Allowing people room to have their "bad" motivations is huge. When you're making decisions, look for and welcome in all the bad feelings you can find.
The "good news" though, is that if you find yourself wanting to make sure it goes a certain way, then you have more weight to place on the side you want to win. This is what I mean when I say system 2 can fetch the other desires and bring them to the table. Why do you want the anchor collapse to go that way - above and beyond what you've already put down? Put that on the balance.
Or maybe you aren't ashamed of it but there are multiple reasons and only the most salient gets brought up, under the false assumption that it covers it all. You might still get the 80% solution which is 80% better than nothing, but you won't be all the way there until you realize "oh yeah, there's also these other reasons".
Or maybe it's just really hard to figure out why you care. Maybe you need to dig several layers deep to get with something you can work with. Maybe you run into problem 1 again over and over as you do this.
For example. If your conflict is "don't want to eat junk food" but "i keep eating junk food", then it's usually easy to get in touch with the wanting to eat junk food. What's it feel like when you're reaching for the junk food? Boom. There it is. But why do you want to stop eating junk food anyway? To lose weight? Why do you want to lose weight? To be more attractive? Why does that matter?
It's not always easy to find out where it grounds out. Not that taking it to a philosophically satisfying ending is always necessary, of course, but you need to be in touch with the emotions behind it - and if it's just a long chain of things that you "obviously should do"... and you can't really justify it with an unspoken oomph of emotions, then you aren't getting anywhere.
And maybe you don't really want to find the answer. Maybe the oomph comes from "and then maybe I won't be worthless" - but who wants to admit that? Because that's bullshit anyway. You know you're not worthless. So to hell with taking that idea seriously!
....and so that part doesn't come to the table.
Or maybe you just have no idea where to even start - "what could I possibly be getting out of feeling motion sickness!? Isn't that a physiological response, not a mental thing?". It often takes some interesting thinking, introspecting, and theorizing to figure these things out. It's fun when ev psych and game theory make sense of things that feel like they "just happen".
Perhaps most commonly is just the lack of understanding of the purpose and necessity of near mode reasoning. You don't have to be running from an aversive reaction, or failing to untangle a complex web of desires. Perhaps you just don't know that you have to be in touch with the motivations.
"Yeah yeah, it really sucks. but ruminating over it isn't helpful so I'm gonna step back and look at this logically. how do I change my behavior?"
Sound's totally reasonable, no? We've all been there. Sometimes there's even use to that mindset.
However, if you keep the possibility in mind, it's often better to say "yeah, it sucks. Do I want to keep doing this?" and gather up everything to place on the balance until you have a decision you're comfortable with.