Talking about yesterday i have lost about 0.01 btc on satoshimines.com not a big amount of money but surely a decent amount for me because i am not the one making big ones in bitcoins,my plan was to make 0.012btc out of them and withdraw after that but my poor luck i lost them all slowly without reaching that target.
really a gamble even you just aiming small wins but if losing streak hit you up you cant really avoid things to happen, much better to limit your bankroll if you are not really a riskier person or stay away if possible.
And it is better if you could track your loses when in gambling you want to make your money, let us say in a basketball season you will just have to set up a bankroll for the whole season and you have to manage that well as when you lose your season is over.