[bueno09]

I just can´t see how you went busto and still thinks 10buy-ins is enough, it isn´t, regardless of your style.
1-Relative size of the bets compared to your bankroll, aka the pressure of bigger bets. It is something that shows up when you move up, because of that (even if u don´t think you do) you will play scared, you will take lines that try for a cheap showdown, when the right play is to get value, you will be afraid of reraise AK sometimes and make big CBs, well, you won´t be able to fully use your skillset to make money.
2-As said before, downswings happens, just for example, saturday i lost 4 buy-ins at NL100, but since i had 26 in my BR, i didnt need to drop down, and didnt play afraid because of that, since you have only 10 buy-ins when you moved up a 4 buy-in downswing (which is pretty normal) is almost half of your bankroll, you will drop down and play frustrated or stay at NL50 and play tilted.
Also, it may not be relevant to the discussion, but since January, i moved up from NL10 to NL100, and all times i mvoed up, my first 5k hands at the level were break even poker, afther that, i started betaing the game at my usual rate, what i mean by this is that i didn´t have diferent skills once i started to beat the new level, the only thing that changed was that the new money didn´t mean a lot to me and i was able to play with confort, not being afraid of paying what was a full stack in the previous level calling a bet in the river.

If u want to see any of my graphs to see the lines of when i moved up, PM me.

Just to make a summary, have 20buy-ins for your current level, even if it is NL25, after some 16k hands you will probably have the bankroll and the experience to play the next level, then mix some tables and move up.

Sorry about my english, it is hard to try to write of something not usual as downswing in a language that is not your main one.

Good luck man!