I agree with both star tripper and Dare.
I would expect SP lasts to neglect or undervalue their security, comfort, mental/emotional integrity or physical health.
I would expect SO lasts to neglect or undervalue their responsibilities, reputation, networks or contributions to something more than themselves.
I would expect SX lasts to neglect or undervalue their passions, close relationships, creative energy, sources of inspiration, and personal fulfillment/satisfaction.
On interactions, I don't know if there's an easy answer. Stereotypes such as SPs being withdrawn or SOs being extroverted or SXs being moody just aren't consistent or reliable enough to judge by alone. Only talking to people and paying attention to what preoccupies them can really give a clue. That said, I think same "non-blinds" are likely to gravitate to each other. In other words, SO (or SP or SX) primary and secondaries are more likely to cross paths due to shared interests.
(but beware those with a 'hidden' dominant type, where their dominant type looks like their blindspot at first glance -- e.g., the SO type that lives alone in a forrest writing manifestos).
Who told you about me?