my domain!

Hmm, so I just got an email from someone wanting to buy my old domain name for the hypnotherapy biz - swiftchange.com. I changed it to swiftchangehypnotherapy.com a while back but held onto the old one just because uh, I thought of it dammit and it could come in handy later, maybe? So, hmm do I sell it? And how much do I sell it for?