You should learn to think big. It's the precursor to choosing an ambitious startup idea, which I also strongly recommend.
However, [thinking small] may make you just as much money. And that's an important distinction. Thinking big and making money are not the same thing. If your goal is to make money then an indie company (like my last one) may be your best bet, or some other industry altogether like finance.
The trickiest part about thinking big is you still need to think small at the same time while executing. You need that grand vision, but you also need to bring that back to today in the form of strategy, goals, priorities and of course your very next steps. Being able to articulate both the big and small in a succinct way that makes plausible sense is a signal of a great entrepreneur.
So actually, Gabriel's initial title ("Learn to think big") is not quite right, as he admits himself, though he mostly looks at the "think small in order to execute" side of things.
I'd focus on the second quote: if you want to achieve some kind of financial success through your startup (which probably should be one of your primary goals for your first successful startup, before you embark on moon shots and change the world), then think small. Think today, tomorrow, next month, think how do we make this fly now. Learn how to make the now work, and when you have that sorted, then cast your eye further out and start to think bigger.
That's the advice I'd give to a not-yet-successful entrepreneur. Think small, focus, make it work, then grow.
If you read this far, you should follow my RSS feed here.