I do think that gamblers who take gambling activities seriously have their motivation come from the amount they envision and hope to win, hence why they remain persistent in gambling instead of quitting after winning a little.
Every gambler expects to win, they want money.
It is as simple as the motivation of most gamblers. If there is no money, there will be no motivation in gambling.
A gambler with a winning amount in mind, gambles much more and can become easily addicted than a gambler just gambling for fun and without a particular winning amount in mind.
Sure, whenever we gamble excessively, it is one step of an addiction. Make a limitation for our gambling activity, it is the only way to avoid addiction. But we must be aware of the bad impacts, in this way we will be serious to prevent from an excessive gambling.
In essence the thought process a gambler focuses on during any gambling activities will determine if such a gambler would gamble much more or lesser than normal and also, if such a gambler would become successful at their gambling endeavors.
Gamble much or less, it depends on the capital of the gambler. How they determine the capital, it will depend on the goal and the financial level of the gambler. Generally, I can assume that much or less will be quite subjective. Someone can say spending $50 is much in a day, other may say it is less. But the right way is to spend small percentage of our income only (below 5% is better).
By the way, it is sometimes difficult to define "success" in gambling. How do you define "success" in gambling? I think very few gamblers who assume the success in gambling is to have entertainment on it. Most of us will determine the "success" based on the amount of money got from gambling.