I do it frequently, even as a middle-aged adult. I think like you, that I might as well go ahead and put myself down before the other person gets a chance to. This is starting to ease up, now that I no longer have people in my life who are very likely to put me down.

Sometimes I end up in a no-win situation, because if I call myself intelligent, then I'm bragging and need to learn to be humble, but if I say I'm not all that smart, then I need to develop some self-esteem, and maybe I should talk to my therapist. I also sometimes say something sarcastically and have it taken at face value. For example, I'm calling another person out because they blatantly ignored something I just said. "Oh, never mind me. I'm only talking to hear myself speak. I didn't say anything worth listening to." Then comes the shocked reaction. "You shouldn't SAY things like that about yourself! You ARE worth listening to!" (OK, then why didn't you?)

Finally, I sometimes hear my husband putting himself down, calling himself stupid or ugly or clumsy, and I tell him, "You'd be all kinds of upset if I said that about myself."