Time and practice. I had a pretty bad crash this spring and it really effected me for a few months. It wasn't pretty on a road bike and my motorcycle. I am still nervous and slow way down on some corners. Specially the one where I lost the front.
What really helped is looking through the turns (harder said then done), weighting outside peg (basically me weight is on it with ass off the saddle), shifting upper body to the inside of the turn (shoulders pointing in to the turn, head turned to look through the turn). As the result you get a better feel for what the bike is doing, decrease lean angle. This increases the amount of traction available for the tires. Relax your arms. You don't want a tight grip on your handle bars. This can provide un-needed input.
I know this is on motorcycle but really a lot of it transfers to road bikes descending at speed.
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