i feel like sticking to certain game types makes a player play a certain style. So if you stick to your bankroll rules and only play low-stake cash games, you won't have the skill set for slightly higher level games or for MTTS, tourney's with rebuy, etc... where the same strategy used in small stake's games will result in losses. For instance, my first times at rebuy tournaments (for 11$) I lost badly because I did not take into account the way rebuy effects player strategy.
so, in general, people get to like 100$ by playing small cash tables and using strategies suited for them --> then lose it.
Play steps so you can get a good sense of different skill levels STTs, that way if you get to 100$ your experience/strategies won't be confined to small cash table strategy.
work your way up to and practice high stake play money MMTs than transition to low stake MTT tourneys, i think the experience from "high stake" MTTS would be useful for low $ stake MTTs.
I don't know if this is your specific problem, but definitely, in theory, something one wants to think about when building a bankroll. That is, getting caught by strategic/experience differences in game types, and how this can effect profit outcomes.