Positive mindset isn't the only driving factor that determines our winning in gambling because one may have the positive mindset and do not make their analysis properly and still end up losing big time. Therefore you are right, good strategies can actually help us alongside with the position mindset + Luck to give us a better winning while gambling, it's also advisable to use an amount that can be subjective or subjected to lose than using amount we don't expect and believing a positive mindset to make a huge a payout, miracle doesn't working in gambling.
When gamblers stake above their means expecting to get a huge reward without losing, I don't know if I should call that positivity or delusion...my opinion here is that whether positivity is in or out of the equation without being disciplined and following principles a gambler would always lose... winning has nothing to do with positivity, it's either a function of skills or luck, these are the two things that actually matters