Eventually, while researching, you'll learn something you didn't want to know. Some fact that ruins a plotline you had in mind. The good news is that sometimes, learning all the facts can make for a much more interesting story than you originally had in mind.
I study orbital dynamics as a hobby. My idea of a good time is sitting down and drawing on that knowledge to imagine a space mission from beginning to end, getting as many details right as I can.
A good plan today is better than a perfect plan tomorrow. Don't wait for an inspired ending to come to mind. Work your way to the ending and see what comes up.
Computer programming is pretty much guaranteed income. I'm good at it, and I like it.