My real name is Sara: a weighty, historic name that still makes me nervous. But that's my mother's name too, and so I was called Sally from the start--partly as a mini-Sara and partly to live out my mother's fantasy of having the sweeter, less intimidating name herself.
As a kid, I thought "Sally" was too hokey for me. And so, around fourth grade, I announced that my name was Sara. It definitely didn't stick.
The funny thing is that now my mom seems to prefer calling me Sarita ("little Sara" in Spanish). And I have come to like Sally precisely for being hokey--classic, I like to think.