I guess I will sometimes bet like this. Let's say I go to a casino and then double my money. I don't just walk away, what I will do is take my principle and then pocket that. I will then gamble the rest of the evening with whatever I have left above my cost basis, which sometimes I lose all of, but other times I end up doubling or tripling, just depending on the situation.
Doubling your capital is getting x2 of it mathematically that's a hundred percent Profit, most people don't realize how huge it is to get 100 percent of your capital...your strategy of using your profit to play is very wise but 70 percent times those Profit will be lost, it's better to double your stake and just leave it, that's a very hard thing to do cause it requires a lot of discipline.. trying to triple or make it x4 might just make you lose everything, I've had experiences were I was supposed to stick to doubling my take but instead I chose to make it x5, I lost a lot due to this.
Self-discipline is key. It can be really hard, but the result is worth it. We are talking not about the profits, but about the knowledge, experience, and perception of the whole process.