A familiar feeling...but it's just slot variance playing tricks on you. When you play slots, you're very likely to lose it all in a short time, and when (rarely) you do build your balance up, that's when you need to stop and withdraw, because with each spin, you're more likely start losing again.
The MG software does not know whether you've been winning or losing, just churns out random numbers for you, and with slots, they're always likely to go against you. Also, if you increase your bets progressively when you win, that also increases your risk of losing it all back in a very short time.
Try jacks or better video poker or blackjack, less variance and therefore your bankroll will last longer.
Sometimes if I hit a good win in slots, I'll just lower my bet and maybe play some
VP to cool down, then withdraw and just leave a little bit for low-rolling.
Otherwise you're pretty much guaranteed to lose it all back in the course of a really bad streak.
Cheers,
SM