I never won any amount in my gambling attempts unexpectedly. Usually I do try with 0.001 bitcoins but before reaching 0.002 I face any long loosing streaks and finding a stop for my gambling. I never was successful to double my bankroll, maybe if I would have tried with faucets I might have won anything unexpectedly.
That is because, we never want to take a high risk, because sometime we feel fear of losing amount and sometime we can't believe on ourself, that we can win unexpected amount. Because main thing in our mind that losing chances is more then winning, and that is true, Because every gambler have a experience of losing, but always pure gambler take a high risk.