Experts treat gambling as a source of income, so they bet on themselves because they’re confident in what they’re doing and believe they can be profitable. These are the ones who raise a realistic bankroll and set realistic targets. let's say on average, if their funds grow by 10% in a month, they’re already happy because over time, it compounds.
Ordinarily, people tend to recommend that you make 10% in savings from your monthly income and should you be earning 10% from your gambling bankroll, I think it’s to the same effect or result which is a good one. For some, it might depend on what your bankroll is but, that’s still positive you know and in a way, you stay profiting. It however shouldn’t motivate you to wish to have a larger bankroll as this is still gambling and loosing can some with such ease that would be regrettable thereafter.