The advice there is specifically about not setting a plan that "if it's not successful in 6 months, I'll go back to this other job in a corporation" - because I can practically guarantee you the deadline will pass without the desired success and it will just make you feel bad, or worse, you might have made a public commitment and then maybe you'll actually go through with it.

So, do make plans about what you'll achieve, but don't make plans to "achieve it in X months or go back to the corporate world".