The sad truth is, that most people think that they can make a living from their hobby, so they try making a business from their hobby. Increasing supply, at same demand means FAILURE. Unfortunately many people, friends, colleagues, or personal trainers recommend doing what you like and you will eventually get successful.
However, this is complete bullshit. Sure, there might be a few out there who get successful by doing what they love, but there aren't many. I mean, how many people do you know that are successful by doing what they truly and deeply love?