How high should confidence level be? High, medium or low to avoid being disappointed but not giving doubt room to get in the way of being confident?

When I'm highly confident about something it just leads me to feeling dejected and very disappointed.

Is there a fine line?

How high should confidence level be? High, medium or low to avoid being disappointed but not giving doubt room to get in the way of being confident?
How high should confidence level be? High, medium or low to avoid being disappointed but not giving doubt room to get in the way of being confident?
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