Welcome!

If by "rationalist", the LW community means someone who believes it is possible and desirable to make at least the most important judgements solely by the use of reason operating on empirically demonstrable facts

You'll be relieved to know that's not quite the Less Wrong dogma; if you observe that your conscious deliberations make worse decisions in a certain sphere than your instincts, then (at least until you find a better conscious deliberation) you should rely on your instincts in that domain.

LWers are generally optimistic about applying conscious deliberation/empirical evidence/mathematical models in most cases besides immediate social decisions, though.