Bring Question

I have a question for about bankrolling. Im sure it's been asked before but it's one of the most import aspects of poker in order to be a successful player. Being able to manage your money for however long your poker career lasts i think is esstential and not even the best of players can come out on top without this knowledge.

The question i have to ask is what is the right amount to have in order to move up limits, being safe from varience. Or is there even a set amount that a new player should rely on. Does the fact that your running very well have any weight in your decision to move up? Also, what happen if you do move up and poker decides to show it's ugly face and varience occurs, how long before you move down, or again is it a judgement call. but even with good judgement is there a critical amount of buyins which force you down even if you know your playing your A game.