Actually, in my (short) experience...
My confidence has decreased. I worry a lot whether or not she really likes me or is just trying not to hurt my feelings.
I actually talk to her a lot less than I used to - I worry that she'll get tired of me. Irrational, I know, but my timid heart isn't listening to my brain.
All the added stress is making me grouchier.
On the other hand: it's fun to be able to say I have a girl. Or she has me, really...