I don't believe in superstitions when it comes to gambling. But even if I don't, many of my acquaintances probably do, but they are reluctant to reveal those things. I have heard anything like the superstition number 5 you mentioned. There, a gambler said that he came across a person who had bad luck at gambling earlier in the day and he guessed that day would not bring anything good for him, which later happened.
That is an interesting one.
We often feel it in our gut when something is wrong or something is about to be. Sometimes it is just that overthinking part in our brain that makes us anxious and think of worst possible scenarios which do not happen because as I said, we are just anxious. But when our fears do come true, it makes us think that maybe our gut was right. Maybe a superstition we did not follow was the cause. But sometimes I also wonder that maybe we keep thinking and thinking of bad things to happen that it gets manifested in real life and our gut feel is validated even if it is all part of a coincidence.