The way I see it, is that if you're new to cash games then that money is going to be disappearing at some stage anyway, whether it be in one massive 300bb stack or over the course of a few 100bb stack. I would really just suggest playing stakes where you have at least 20 buy ins for the level never ever ever ever play with scared money it's how you lose. Play a stake where if you lose a buy in it wont matter at all.
Normally I'd say stay at a table if you double or tripple up because you're probably against a bunch of fish, however because I get the impression that you are rather inexperienced, especially at cash, I recommend that you leave the table when you double up because you are likely to make a large mistake that will cost you 200bb, and the lesson you learn from the loss could just as well be learnt by losing 100bb.
Hope that makes sense. Leaving the table will essentially save you money on the mistakes you are going to make as you learn cash games.
Feel free to dismiss my post as drivel if it doesn't apply to you.