Of course, everything involves luck, and no matter how well-developed a strategy, even by experts, it still doesn't guarantee consistent wins, and the percentage of losses will always be greater than the percentage of wins.
Indeed, it's best to bet or play games you've mastered and capitalize on the high odds of winning by placing large bets, and vice versa. And even if you win less than you lose, you're still capitalizing on those odds by placing large bets.
In gambling, gamblers can believe they are genius and have excellent gambling strategies for winning and even beating casinos but the general fact is most of gamblers lose money while casinos become bigger and richer with time. There are winners in gambling but in general, gamblers can not beat casinos and can not easily win a lot of time and take out money of online casino too easily as if this is doable for gamblers, all online casinos would have been bankrupted by running out of money to proceed withdrawals of their users.
You can think you already mastered a game, had a winning strategy but never bet too high on that winning strategy. With gambling, if you are over confident, bet high, and hope high, you can lose big and even lose all of your money.