A TRADITIONAL "JOB" ISN'T MUCH MORE SECURE IN THE LONG RUN

You might be a great engineer or marketer. You could get a high paying job right now. Add in some perks and things sound great. But here's the truth: no job is safe in this world. At least doing a startup is some function of having survival that is within your control. When you're fired, that is usually it. When you go through the equivalent of "being fired" in the startup world, you can fight back. You can persevere and stay determined.

THE WORST THAT CAN HAPPEN, ISN'T REALLY THAT BAD

It seems a lot worse when you think about it now, but it really isn't that bad. If your startup fails you will hurt afterwards for a decent while physically, emotionally, and financially. People have been in far worse positions and triumphed. If things fail you either a) try something new startup wise b) join another company whose mission you believe in c) take a new direction in life. Failure at a startup DOES NOT mean failure at life.