I think some of the many people who gamble out there do gamble as a hobby and have reasonable limits that are set.
We do hear this often times.
Everyone who gambles for money will be disappointed because it's unlikely that they'll hit their goal on a daily basis and compare it with their daily rate from their employment or jobs.
That's why, gamble only with the aim of having it as a hobby and to have fun. Limits should also be there and don't gamble with what you cannot afford to lose. It'll make you crazy when you lose it and you'll get into that cycle that you'll have hard time to break.
You are right. Spend only the money you are willing to spend for your own entertainment and don't forget about the emotions that may arise either from a big win or a really bad session. It's essential to stay self-disciplined.