I don't see any reason why should get their hope high in gambling, when you are fully aware they you winning is boils down to luck . Which means you can either win or lose . So not getting your expectation high would help in relieving the stress in gambling. And would help one to approach gambling in the right way , because most time alot folks always get their hope high in gambling because they believe they can get rich through gambling fast which may also trigger some sense of gambling addition too.
Yes because planning to spend money from winnings when the winnings have not happened is something that is not realistic, and the only reason why putting hope on winning is really always not recommended in gambling is because the results are not yet known about whether you will win or lose, it is actually okay to make a plan regarding how you will spend money from winnings if you have seen that the results are really winning in the sense that you have finished the session, but if the results have not come out and you have made a plan to spend money from winnings then it does not make sense.
I think it is a fact that putting high hopes on winning in the end will only increase the feeling of disappointment when the results are not as expected, it is very possible for you to end up getting caught up in emotions and various impulsive actions when the results are not as expected, so if the results have not come out then just assume that losing is still a possibility when the game is over.