Quote from atticus:
It's no different than casino gambling. If you're winning at gaming then you should move cash off the table, unless you're gambling at edge (counting at 21 into a high count) in which bet-variation is critical (increasing bet-size into high 10-factor).
It's why Kelly is worthwhile in trading as long as you can quantify your edge. Bet-size should be kept proportional to stake unless your edge is large.
Nice, always thought it was more like blackjack myself.