How do I handle the fear of being wrong with big investments?

You are moving enormous sums on bets that mostly fail, and the fear of being wrong never fully leaves. That fear is not a flaw in you; it is an accurate read of the job. Anyone doing this without any fear has stopped taking it seriously. But notice the shape of your work: in this game, most individual bets are supposed to fail. Being wrong often is built into the model. The measure is not whether each call lands but whether your judgment, over many calls, comes out ahead. One loss is not a verdict on you. It is a data point in a long series. Separate the decision from the outcome. Judge yourself on whether you reasoned well with what you knew, not on whether the dice fell your way. Keep a record of your thinking at the time of each bet. When fear spikes, that record reminds you that a good decision and a bad result can live in the same story.