Back-up plans are an excuse to fail.
Say you want to be a movie actor. With all your heart you want to be an actor, it's all you've wanted to do.
What would you do? Would you move to Hollywood as soon as you can, take acting classes and start auditioning right away?
Or would you go to school for a degree in whatever just so if you fail at acting you can fall back on something?
Conventional wisdom says you should have a backup plan, just ‘in case'. That you need insurance against a lifetime of failure.
Conventional wisdom is for conventional people. They accept their choice of backup plan because they know they are going to fail and apparently they are ok with that.
The reality is that if you accept your backup plan and live that life you are a monstrous failure. You are a failure because you gave up on yourself, because you didn't believe in yourself, because you refused to let yourself succeed.
When you have a burning desire and you put all of your energies into making it a reality the truth is that you cannot fail. Failure is impossible, beyond impossible. It isn't even a thought.
Ah, but when you have that back-up plan still lingering in your mind you aren't truly giving 110% to achieve your goals. Maybe you're giving 75%, even 95% but that isn't good enough. It takes 100% minimum.
Kill your back-up plan and put all your energy into becoming what you truly want to become. If your burning desire is to be a Doctor, great, go for it.
If your burning desire is to be a traveling fashion photographer, great, go for it. Is your burning desire to be a salesman or an office drone or a substitute teacher? Probably not.
Burn your bridges. Pass the point of no return. Give in to your desire with all your heart. You cannot fail. It's impossible.