Should you start left-foot braking on your way home from work today?
That's a giant no. You've spent a long time getting used to braking with your right foot. The first time you try to stop with your left foot, there's a really good chance you'll slam on the brakes -- the amount of pedal force required to stop is a hell of a lot less than you think it is. Learn somewhere safe, like a parking lot. Practice there quite a bit, then progress to residential streets, just like when you learned to drive the first time.
Also, don't do this in a car with a manual transmission, since you need your left foot to push in the clutch.
One final caveat: statistically, the older you are, the more likely you are to have difficulty switching up your braking patterns. I started doing so in my late 20s, and it felt absolutely second nature within a couple weeks. If you're 50, it might not be so easy. Ideally, you'd learn from the first time you drive, but because some states will (incorrectly) fail you for using your left foot, you can't. You should still start teaching yourself the technique ASAP -- or don't cry to me when you rear-end someone.