"Bankroll" is usually a term used in sports betting. From what I've read in some of the threads here, we need to be disciplined in managing our bankroll, typically betting only 5% to 10% per wager. So I'm curious: do bettors here really set up a bankroll first before they start gambling, or do they just gamble whenever they have available money?

Please share your experience whether positive or negative and what you learn from it.