Not sure what “don’t worry about what your are doing” is meant to address. If you think you can do better at something with worrying, that’s one thing. But if you think you can do well at something without putting some real effort into finding solutions and excelling, then it’s bad advice.
Worrying is nothing more than an emotional reaction. It doesn’t necessarily lead to the right “solutions.” Worrying is more likely to have a negative effect, especially when parents worry about things they shouldn’t worry about. Sometimes, the right “solution” is to relax and stop worrying so much.