I agree with the idea that if you know nothing about a topic, it makes sense not to set goals in that space before you know whether those goals will be achievable or not. But Dan's advice is given with the caveat that "The advice from now on will assume that you know at a very high level what you like, what you're passionate about, or where you want to go" -- and in any case I disagree with the notion that just trying a task for awhile with no end goals is a good way to accomplish something. (It is, however, a reasonable way to discover possible goals, which may have been more of what Dan was getting at.)