Discipline is the hardest part of gambling, whatever form, whether Poker, Sportsbook, Casino etc etc. It's lack of discipline that creates problems for people and their fun can turn into an addiction.
My advice to anyone looking to have a gamble is to recognise how much they are comfortably able to lose and then set a goal which is they achieve will be the stopping point for the session. If the money is lost then they should NOT go back and deposit more. Try to look at gambling as a recreational activity and to convince yourself that if you lose, it's ok, it's money you can afford to lose anyway.