The health effects of stress are pretty insane, I actually had to stop hacker ranking the other day because I noticed my blood pressure would shoot up by about 10 points.
You can practice until the nerves are gone. I've been doing Leetcode weekly competitions, after a while it's just another timed coding challenge.
I've noticed training cardio helps me handle anxiety better, both because I can better handle the physical effects when they arise, and the training itself removes anxiety I'm feeling at that moment.
It's not just that, it's the fact that you're preparing for a job interview which is already a stressful endeavor. When you add oh my God I need to learn all these new things, I need to solve these algro problems faster, it's just too much.
This is exactly why I opposed any sort of leaderboard idea at my previous job. Work can be stressful enough. Let's not make it any more than it needs to be.