I think "untrue" is maybe too strong if you equate it with a lie, but I take it precisely as your meaning of incomplete. And it's not even that it's a deliberate untruth--on the contrary--it's just that nothing can be conveyed completely, if for no other reason than that your own thoughts and ideas and feelings and interpretations and impressions are always changing.

But, it would be a sad world if we didn't **try** to communicate, so yeah, in the end I come down on the side of expressing yourself, even if the expressing never is quite true. And I do agree, too, that you can often learn something about how you're feeling by trying to articulate it.