It doesn't matter whether we are talking about sports betting or online poker playing; money management is not an easy thing to practice. It takes real discipline not to chase after losses and to walk away when it is not a good day.
Practicing good money management when playing online can be even more difficult. The games move faster, the players are looser, and the games are typically more reckless. This leads to poor money management. Another factor when talking about online poker is that it only takes a click of a button to add more money to your bankroll. When playing in person you at least have to get out of your seat to go to the ATM.
When we talk about money management we first have to talk about bankroll. Whether you are playing for recreation or for a living, a bankroll is necessary. When you practice sound money management, and remember that very few people do, it is best to only play with 10% of your overall poker playing bankroll in any one session. The biggest advantage to only bringing 10% of your bankroll to the table is that you can't lose more than that 10% if things go really bad. And remember you should be playing at a comfortable level where you still have enough chips to do some damage. If that means playing at a $2/$4 table instead of a higher table, so be it. It is better to win small than lose big.
here are many people that are going to ignore virtually everything we have talked about concerning money management. We can talk all day about not playing above your head or taking the proper bankroll to the table, but the bottom line is that most people are going to do just the opposite. If you can take just a moment to consider bankroll, proper level, and session size, then you will be ahead of nearly everyone at the table. That doesn't mean you will be winning during every session, but it does mean you will be more prepared, and that is a positive step toward winning at the poker table.