This could be another superstitious belief or a gamblers fallacy that being positive might help you win, when it fact it will not, and that's why there are games that are based on pure luck because you don't have control over the results.

So even if you go 100% being positive on the next spin for example, it won't affect the result, it's good to be positive, so that somewhat we have something to lean on but in any case the result is going to be bad. I guess just play and have fun and maybe if you get lucky and not greedy, at the end of your gambling session then you might have a good money in your wallet.