Your results prove nothing
My results prove otherwise.
Your results probably fall within the expected range.
Suppose your expectation is -0.5% and your standard deviation is 1.13 per bet (approximately number for bj). If you've made 10,000 bets, 99% of time (3 standard deviations) your result will be between -389 and +289. Note that there is a relatively high probability of being ahead at this time. So, it is quite possible that your outcome so far has been the result of fortuitous luck.
However, as you play longer, the percentage of the range that's in the negative will increase. Eventually, the upper limit of the range will be negative. Here are some numbers*:
10,000: -389 - +289
40,000: -879 - +478
160,000: -2,156 - +556
459,684: -4,597 - 0
640,000: -5,912 - -488
Note that 459,684 bets is equivalent to about 4,600 hours of blackjack.
If you have the advantage in your favor, as with card counting, the opposite happens, i.e., as you play longer, the percentage of the range that's in the positive will increase. Eventually, the lower limit of the range will be positive.
* The formula: Low limit = n*-0.005-3*1.13*sqrt(n), High limit = n*-0.005+3*1.13*sqrt(n), where n = number of bets, -0.005 = expectation of 1 bet, 3 = number of standard deviations, and 1.13 is standard devation of 1 bet. Actually, I should use sqrt(n-1), but that would make the numbers messy, and it makes little difference for large number.