So, this is going to be martingale in sports betting? I doubt it that it's going to work.
The typical martingale in dice and other luck based games don't even work in the long term. And that's why give up with this idea if you don't to burn your money.
But if it's the opposite, good luck with what you're doing.
This is sportsbetting, so it is different from the regular casino games. Consider each match or game that you need to bet. You should know the sports well and very familiar with the athletes involved. In this way, you have better chance of selecting odds which has higher potential of winning. If you don't know the sports, you are just betting blindly and losing is inevitable.
The role over you are talking about, are you referring to spending previous winnings on gambling instead of withdrawing them? If that's what you mean, a most of gamblers don't withdraw after winning; they continue gambling until they have won more than their previous balance or until they lose all the balance. Personally, I take my profit without hesitation as soon as my game is successful. I only keep a small amount from winning, which I will use for next time, but sometimes too, I lose everything, and there's no balance to keep.
That is actually true. Most gamblers will try their luck to hit more winnings. Thus, they tend to continue their game even after winnings. Unfortunately, most will lose what they won. And they will only regret it once they totally lost their bankroll. If you want to have an assurance, it is always best to withdraw some winnings and just leave what you think you are more than happy to lose for that session.