Unnecessary worry though, is unhealthy.....for you AND them.
To some degree, worrying can CREATE an energy that allows the "feared thing" to happen.
So, don't give it any energy. I was always mindful of my thoughts while my kids were growing up.

Both my kids got stitches when they were little.
My daughter got a scar on her beautiful face when she was young, and I knew she'd have it for life. Considering she's a covergirl, we laughed about it over Christmas.
I reminded her of how she got it, and that she had done something I told her not to do; therefore I was right all along. Then she and her brother told me what REALLY happened and how she got it....20 years later! (It was worse than I thought!) So they can conceal things too. You have to have a ready ear for them, and help out only now and then.

Kids will do what they want to do. They'll either learn and slow down and start to gauge the consequences, or they'll speed up and test it at every turn. For those who've raised kids, know it's the most character building experience (if you actually survive it).