Ever wonder something like, "I know it's bad for me that I lost my job, but I actually feel happy about it... is that rational?"

What could a question like that mean?  There is a divisive ambiguity here that really messes people up.  A feeling as an experience is neither rational nor irrational.  It's like asking how ethical a shade of purple is.  The point is that a feeling must be framed as a behavior or a statement to ask whether it is rational, and which one matters heaps and loads to the answer.

If you think of the happiness as a behavior, something that you're doing, then the question is secretly asking about instrumental rationality: whether you're applying your beliefs correctly to attain your values.  In our opening example, the question becomes "Does feeling happy serve my values?", or simply "Do I value feeling happy?".  If you're almost anyone, the answer is probably "yes".

If you think of the happiness as a statement or instruction that says "Your values are being served", which can be true/false and justified/unjustified, then the question is really about epistemic rationality, and asks: "Am I justified to believe my values are being served?".  If "it's bad for me" means "no", then "no".

Because of this ambiguity, although it can make sense to say "I'm happy" to indicate "my values are being served", I propose that in the interest of epistemic hygiene it's worth being more specific.  Conflating feelings-as-behaviors with feelings-as-statements inflicts a great deal of pondering and confusion about whether feelings are rational (also precipitated by Hollywood), and to make matters worse, each of these similes has only limited validity: