Every decent poker player has gone through a tough run of cards and has lost a lot of money despite playing well. THis is just part of the game and will happen to everyone. Luck is an inherent factor in poker and it's important to note that difference between the good players you see time and again and those who disappear into obscurity is usually bankroll related. A good player can be wiped out by a run of bad cards because of poor bankroll management. And many a professional poker player has gone broke due to bad money management, by playing limits where their bankroll can't compensate for the swings in fortune.
It's a somewhat different story for beginner and amateurs. Usually it's not just a bad run of cards which cracks a player, most of time it involves players running before they can walk by playing at a higher limit with an insufficient bankroll and skill. If we're all being honest, most players including myself have tested higher levels before we were ready and have had our fingers burnt. It then takes a lot of time build up the bankroll again at the lower limits while simultaneously moaning about bad beats we've suffered. The end result is that you learn an expensive lesson, but one which stays with you! Here's some beginner advice to avoid you making the same mistakes!
Playing in a game with an insufficient bankroll will leave you vulnerable throughout the game, and will not allow you to play your best game. You'll be far too preoccupied in not losing all you money, you won't realise how tight you're playing and before you know it you've been bluffed out of your money or been outdrawn for all your buyin.
If you are a no-limit player you should buy into a game for no less than 100 times the big blind. So if you want to play $0.10/0.25 No-Limit your buyin should be at least $25 and that buyin should represent 5% of your enitre bankroll, never any more. This sounds excessively conservative, but you'll find out sooner than later that it pays off being conservative. From then on whenever you want to move up a level make sure you at least 100 times the big blind of the buyin and at least 10 buyins after that (i.e. sit down with $50 for 0.25/0.50 etc. and have a total roll of $2,000.
If you want to start off playing a Sit N Go tournaments as a beginner you should have a bankroll of at least $200 and play in the $5 + 0.5 SNG's to build your bankroll. This will give you a exposure to semi-competent players where you'll learn a thing or two, but where the game is reasonably beatable just by reading some SNG strategy (be sure to check out our Tournament Strategy section). This will hopefully let you build you bankroll gradually and protect you from any bad beats you may suffer.
The best advice is not to run before you can walk. Play well and move up only when you have the cash. By playing games that are within your limits you give yourself a much better chance of being a winning poker player.
Good luck at the tables