Basically, happiness is understood as a strong, positive feeling. The term originates from the Middle Ages, where "luck" meant that something would turn out well. Since happiness is always a personal feeling, the term can also be described as "subjective well-being".
It can mean either a short period of time that makes the person happy (e.g., a fun evening with friends, a nice date, a big win at the slot machine). Or it can mean a long-term state that is normally aspired to by all people (e.g., physical health, financial independence, intact family life).
In gambling, happiness is generally of a short-term nature. This means that while the joy of a big win is great, it is not long-term. After all, the next round of gambling is bound to start - and by then the emotions are usually neutralized again. Of course, the fulfillment of human desires and aspirations cannot be found in gambling.
Nowadays, there are many terms associated with luck. These include, first of all, clovers with four leaves, horseshoes, ladybugs and chimney sweeps. It is not uncommon for these very "lucky symbols" to be used as winning symbols in slot machines.