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.
When we are playing a game of luck and have high hopes to be able to win, it is very stupid because we will never know the result we will get until we finish the game, which you say is very correct by not putting high expectations on the bets we play, it can reduce the disappointment when we do not get good results from the gambling.
If someone thinks that by doing gambling will be able to make them rich, of course this is very incorrect and most of those who think that gambling is easy to get rich they will continue to gamble and it is not uncommon for us to see them will be addicted to gambling.