In real, face-to-face, table-based poker, the cards are always random. In the land of computers, the cards are a lot less random than you might think. That doesn't mean that there is a person in the admin seat dealing you off the bottom of the deck. It's all automated, and online poker companies pay a lot of money to license some of the most trustworthy and dependable poker room software available. Poker has assumed a new guise of integrity and sportsmanship, on top of sharky competition, and that includes extending its presence to the internet.
However, the inherent nature of computers brings with it a limitation: there are no truly random numbers. A computer must always start with a certain number selected from a select range of numbers and then perform calculations on it to randomize it. What this means to the online poker player is that "streaks" of either monster cards or hopeless hands are more likely to occur and linger.
You can't futz with the software to tweak those numbers in your favor, and we're not suggesting that you try. Unethical behavior makes the game less enjoyable altogether and completely removes the sense of sportsmanship and integrity that poker deserves, despite its shady and romantic beginnings. But what you can do is be aware that those shortcomings so that your bankroll doesn't become the victim.
If you're getting a string of bad cards and it seems like you can't get a break, just pick up and move to another table. This ultimately changes the dynamic of the table and rolls another number for you, starting you afresh. Even if you've picked up hints and tells on how other people at the table play, you don't have so much at stake at one table that you can't leave. Switch to another table and see if you fare better there.
Conversely, if you're on a hot streak, don't leave until you're sure you've run dry. Online poker is a fast-paced game with players coming and going. Often the streaks of luck from those not-quite-random numbers are disrupted frequently enough that it doesn't matter. But it's better to be aware of those shortcomings than to let them affect your ability to play altogether.