Referring to the February incident, Brown said on "Larry King Live" Wednesday night, "When I look at it now, it's just like, 'Wow, I can't believe that actually happened.' It just really, like, took a toll on me."
Brown faced the music in his first televised interview since being sentenced to five years probation for the assault.
Brown told King, "I guess that night is one of the nights I wish could I take back, and (that) I really regret, and I feel totally ashamed (of) what I did."
Brown expressed remorse and took responsibility -- all under the sometimes tearful eyes of his mother, Joyce Hawkins, herself a victim of domestic violence.
Hawkins told King the experience has been "the most painful time." She said, "It's been hard, really hard, seeing him going through the pain and everything that he's gone through."
And though Brown has been ordered to avoid contact with Rihanna, he professed his love on the show, saying he is "definitely" still in love with her.
Brown repeatedly said in the interview he had difficulty believing he did what he did.
In reply, National Organization for Women's president Terry O'Neill issued a statement saying, "It's all too common for offenders to claim they are 'not the kind of person who would do such a thing.' But when we allow them to evade responsibility by redefining themselves in this way, we trivialize their crimes and jeopardize their ability to heal and stay safe."