When to Quit!

I always seem to have this problem of building a decent amount of money throughout the day then losing a good portion of it on a few bad beats. How can I avoid this and when is a good amount of your total bankroll to be up before quitting for the day?

if you'll can help me with this issue it would make me a good amount of money.

I dont know what site your playing at, I personaly like to play on Fulltilt. But I have found its best to bring only what I am willing to lose, and I will leave a table once I have either doubled it, or lost half. Im guessing that you are bringing too much money to the table. Hope this helps. Good luck to you in your gamming!

Do now quit when you're up; quit when you feel you are losing your edge.