You sell in TN now, right? You're previously from the area you're moving to, right?
So you know areas/neighborhoods and your way around... why do you say "starting over"?
The laws for CA and TN are different but not considerably. The MLS software will be a little different but essentially similar. The day to day execution is pretty much the same and I'm going to assume you knew people when you lived there before... although I don't know how long ago. You're going to have some relationships to "kick start" your career when you get there and you'll be able to do all the same day to day executions to run your business there that you run in TN now - plus referrals from your current office (or other TN offices too) to the SCA area.
It's not like you won't know where to start your day.
Forget about a slow market - in S. Cal you only have to sell one home for every 3-5 you have to sell in TN.
Do you grocery shop ? Have kids? Work out in a Gym? Go to church? You'll be fine... ; ) Meet your neighbors and get busy or work with a team when you get there for a while if you think you need to.
RE the other post, I too WAS with Keller Williams - for one year. There's a reason why. Look hard and ask a lot of questions before you make that move. No, I'm not trying to discourage you, just make sure what works for those other agents works for you. The book is worth reading - and they will give you one free for interviewing - just ask a lot of questions first.
Good luck to you!!