“Just do it” is stupid advice.

Nobody hears “just do it” and then “just does it” unless it’s easy enough for them to “just do it,” in which case they don’t need to hear it in the first place because they can “just do it” whenever they want.

Before you can just do it, you need to believe that you actually can. Start on a smaller scale, for example, or talk to somebody that did it before. Once you believe that you can, then you can also just do it. No condescending advice needed.