Life, like any organic process, is an uncertain affair. You can guide it, but you can't control it. You might lose your medical because you've had a stroke and are half paralyzed, and your plan B of being a professional basketball player is right out the window.
When you invest, if you invest, do you invest in two stocks—most of your money in the one you think will do well, and a little bit on the side into a different stock in a different industry?
I mean, maybe you do—who am I to judge?
Invest in yourself. Engage in ambitious polymathy; acquire knowledge and new skills and never stop pursuing interests. You never know what tomorrow will bring.
Let me simplify that:
A plan is a tactical endeavor. Having a backup plan, by itself, is almost worthless. "No plan of battle survives its first contact with the enemy."
Contingency planning is a strategic endeavor. Not one simple road that leads to victory and another that protects from retreat, but a structure of support and tendrils of growth, like roots and branches.
-Fox