Well, for starters, there are about a million+ threads in this and other forums about bankroll management. Try this one first.
ajmargarine: 'Bankroll and Moving Up'
I found it in the
SSNL Master Sticky - ALL POSTERS MUST READ
I think your biggest problem is not understanding and applying good BR management. Even if you are great, there will be variance. You need to be able to have the BR to cover that variance without changing what is otherwise a +EV (I hope) style of play.
Second, never move up after big loses. Always move down and grind your way back up to where you were.