Some of the worst career moves I've ever seen are by people attempting to "be themselves."
The old advice of "To thine self be true" only works if thine self is a reasonably pleasant and productive person. Unfortunately, that line has been used by many a lout or slug to justify worthless or offensive behavior.
These individuals use "I don't feel like it" as if it is holy writ.
"You don't feel like it?" What does that mean?
You routinely offend your co-workers, but that's no problem because you don't feel like being polite?
You missed the deadline on the project, but it should have been extended until you got in the mood?
You dressed like a slob for the client meeting but they shouldn't mind because you were just being yourself and not a phony.
A large portion of history's advancements was achieved by people who didn't want to be achieving them. They subdued their natural tendencies to sloth, vulgarity, pleasure, or abrasiveness and did what was necessary to establish effective relationships and get the job done. While toiling away, they often encountered challenges and attacks that made their tasks most unpleasant but they kept at it.
In doing so, they made their "selves" better and improved the lot of many others. They put a devotion to duty and higher standards above an "If it feels good, do it" attitude.
They would not have accepted "I don't feel like it" as the final word on how they should behave.