Also, feel oneself. Sense oneself as being in a normal state of health or spirits. For example, I'm finally over the flu and feel like myself again, or He doesn't know what's wrong but he doesn't feel himself. The antonym is not feel oneself, that is, “feel unwell.” [Mid-1800s] Also see feel up to.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.