You probably play too conservatively. This is the reason why 80% of blackjack mistakes are made, even among high-stakes gamblers:
This paper uses proprietary data from a blackjack table in Las Vegas to analyze how the expectation of regret affects peoples’ decisions during gambles. Even among a group of people who choose to participate in a risk-taking activity, we find strong evidence of an economically significant omission bias: 80% of the mistakes at the table are caused by playing too conservatively, resulting in substantial monetary losses. This behavior is equally prevalent among largestakes gamblers and does not change in the face of more complicated strategic decisions.
Source: “Fear and loathing in Las Vegas: Evidence from blackjack tables” from the journal “Judgment and Decision Making”