Solid players are disciplined players that don't just risk it all away. Solid players are always aware of their money management and their bankroll. In fact, even if you do set out a certain budget you will see your bankroll increasing as you make fewer mistakes and safer wages.

First of all set a goal in terms of money management. For instance: "I will not play more than $50 this week" or "if I lose the money in my account I will not reload tonight as I'll probably be on tilt and making bad judgement calls". A few goals like these will save you lots in the long run. Remember, money management is not about being tight, it's about making the right decision.
Another standard you should set is how much money you want to play and for what limits. If you're playing poker for instance and your bankroll is $100, you'd like to be playing $0.05-$0.10 or $0.12-$0.25 limit. Only when your bankroll grows to say, around $300 you could play $0.25-$0.50. Actually if you're losing money you should play a lower limit. Try it and you'll see the difference.

When asked what is the most common mistake that casino players make at the tables, famous poker player Phil Ivey said that they don't know when to leave. That is, they either leave too soon or too early. The secret is to set a win goal but also a limit for your losses. It's a mistake to win and leave too early with too small a profit as it is a mistake to leave to late after you've been going on tilt and losing everything on avoidable mistakes.

Take advantage of casino promotions! More often than not online casinos will come with interesting offers and some of them are so profitable that it would be a shame not to take advantage of them. Remember, when joining a new casino look for one that pays a high registration bonus. If you get promotional emails from your casino get in on the action with their special deals. Some offers are about rewarding active players, some are just plain luck sweepstakes.

Save a little here and there. When you're winning, put some of the profits in the piggie bank and leave the rest with your bankroll. Most people play in casinos for entertainment but if you think it's more fun to win then pocket some of the money. It's common sense.