AFAIK Rationality is in philosophy intelligent pursuit of self interest. Value in life stems from having feelings. People are a "locus of care" for the value of being, which is an emergent, evolutionary designed, existential modality. Because there is value there is dignity (innate worth, {+ or - mental states}) and preferability of some states as compared to others. A basis for moral choice and moral concern.
Because some mind based existential states are preferable to (or better than) others they
ought to be pursued. This is a reasonable or rational response to dignity, ie it is
dignified. This is deontologiccallly logical, because it is morally logical to pursue the better ethical option.
Where there is logic there is truth and rationality. Preferable or better states (internally) ought to be linked to adaptive and well adjusted behaviours (externally). Because they in the long run are the cause of benign mental states.
This is basically what rational attraction to being is: liking being - happy existence - whilst being behaviourally adjusted as an organism.
It has its existential dimension ("yippee life!") and its biological one (flourishing physically, or health) and behavioural or cultural one (rational and adaptive cultural traits and behaviour).
Conscious zombie: I think that the objection "rationality does not relate to feelings or desires" depends on Aristotolian concepts of logic, rather than
deviant / non standard modern logics. And on the old fact / value distinction which came before Husserls phenomenology of emotion (where we have phenomenology of value) and basically treated the inner life as not quite factual , i.e. only the "object domain" counted.
You may think I am inapropriately borrowing the term "deontology" from Kant, but in fact it was Bentham who came up with the term.
I have written a 10 page essay on this if anyone wants an email attachement sending.