A great point, that I haven't seen in too many places. I sometimes feel like we're seeing too many people who "want to have a startup" for the supposed fame and fortune, and not enough who are truly passionate about an idea. Believing in an idea will get you through, not dreams of gold coins.
Sam, I noticed you didn't mention watching cash burn or unit economics. Is that a later section you might add? Too many founders don't realize the importance of that until it's too late (speaking from personal experience)
I think to really succeed at a startup is to make a product that is needed and that can be sustained throughout the years. To do so, you have to think long term.
Its ok to add the "new hotness" to your business as well, but it shouldn't be what the core business is about.
Facebook's success was not because they added photos, IM, pokes, likes, it was because there was a solid platform to find people. Sure those other features helped promote and enhance the product, but without the focus on the #1 goal (making it easier to connect the world) that platform could have easily gone by the wayside.