Yeah, that's exactly what variance is, and yeah, the laws of variance state that you're supposed to win and lose a certain amount of the time, which should tell you that the random aspect of poker( any two cards can win) is a fundamental cornerstone of the game, and must be respected. Therefore, you must adhere to strict bankroll management rules, so when the inevitable suckout or ridiculous preflop call pays off for your opponent, your roll won't be too badly affected. Bankroll management is one of the toughest concepts to stick to, because everyone wants to win as much money as possible, but everything any of us has ever learned about poker applies to the long run; the odds
of success/failure over many tens of thousands of hands played or more. Your roll should reflect that by being able to withstand huge swings over long sessions. Two percent rule.