Everyone else has already said it, but I'll try a different way. Understand the odds
. Even when you are a "heavy favorite" in poker, it's usually not more than an 80% favorite. So, 1/5 times you will lose. Most times, even as a "favorite" it's even lower than that.
Further, you have to understand that the odds even out over an infinite number of hands. "One night of playing" is not "the long run". Even a month of playing isn't long enough to see a true statistical outcome.
Combine that with the fact that people seldom remember the 4/5 when they DID win. They remember the 1/5 losers. And take them harder. They also don't remember when THEY won with the "2 outer". Only when they lost that way.
Remember, there are ALWAYS short-term anomalies, in person, online... ALWAYS.