You have brains in your head. You have feet in your shoes. You can steer yourself in any direction you choose. You're on your own, and you know what you know. And you are the guy who'll decide where to go.
I didn't realize this when I was about 18 or 19 and trying to decide "what to do with my life"; I thought that choosing a major meant determining my fate FOREVER. This mindset sounds a bit silly in retrospect, but at the time, I think a lot of my classmates felt similarly.
Fortunately, life is like a river in that changing its' course can seem daunting, but with time, effort, and ingenuity, changing the course is doable.
As Dr. Seuss said in the quote above, "you can steer yourself in any direction you choose." That's a pretty important thing to remember, whether we're 18 and deciding on a major or 28 and deciding on a new career venture : )