I think that it is possible that somebody can study something so much that they never actually do it. I think that some people are so intent on making sure that they know every detail of a subject or topic that they never actually end up using their knowledge. I think that people need to know when it is time to do.
Studies have shown that it's not just how much you study, but the way that you study that leads to long term comprehension and mastery of a subject. You should study a little bit every day so that you have to commit the information to your long term memory in your brain.
Yes, a person can study something so much that they never actually do it, because learning about something and doing it are two different things. A person needs to be able to take a risk. Put the book down and get out of your comfort zone. Some people are perpetual students. That is a good example.
I do not believe you study something so much that you never actually do it. I don't even know what that means or why someone would go about studying something. There are many things you can study without doing anything. History is a good example of this. Study all day, all you'll gain is knowledge.