I think that's an interesting way of putting it. I guess I don't think of the SI as something separate. It's a part of you; one of the voices within you. If it's kicking in, there's a part of you that wants to stay, even if that is just a biological instinct.
We often have other instinctive voices within us and often make the choice to override them, using whatever criteria seems to make sense to us at the time. Think of a bride having wedding jitters on her wedding day, even if she's marrying the love of her life. There's always some element of fear of the unknown. But in those cases, more often than not, logic points them t going through with it.
So if you have last minute regret, perhaps it's not best to just try to shut it out, but use the opportunity to confirm for yourself that, despite any possible reservations or fear of the unknown, this is the best course for you.