The Basic Rules
The habits that keep betting recreational are unglamorous and they work.
Decide what you can afford to lose before you deposit, and treat that amount as the price of the entertainment rather than an investment you expect back. Set a time limit as well as a money limit, because sessions expand quietly when a match is running. Never bet with borrowed money, money meant for bills, or funds you would be uncomfortable explaining. Never chase a loss, since the impulse to win it back is what turns a bad session into a serious one. Avoid betting while drinking, upset, or under pressure, and take regular breaks rather than betting continuously through a long fixture.
Keep your own record of deposits and withdrawals rather than relying on a feeling about whether you are ahead. Most people who believe they are roughly even are not.