Saying we aren't rational is not an argument that philosophy cannot improve our lives. In ancient Greece the latter used to be an important part of philosophy. I think schools such as stoicism and epicureanism have a lot to offer.
That is, if rationality is optional, to be put aside when it doesn't suit us.
Or if rationality is an expression of an underlying form, like a glove over a hand.
Then, if we want to address a person, to influence him or whatever, then we would do well to address that fundamental form and not that optional, superficial expression.