Someone said "Learning what you don't want to do is pretty valuable, it may be as valuable as figuring out what it is you do want to do." Opinion?

Let's use careers as an example. Rarely does a job entail what we think it does before we try it for ourselves. If you try a career path and discover its not the job for you, then you've learned something valuable. Perhaps a summer working with a lawyer will save you from years of law school before you discover the hard way that law makes you miserable.