Both. There's a lot of dumb luck in this world, and me being a software developer at just the right time was luck.

Working smart, living smart, also makes a huge difference. Every 83/month you save off your expenses (rent, more efficient transport, better utility deals) is the same as earning 1k/year more after tax. At lower income levels (but not the lowest because at the very lowest people don't have a choice), investing that over a lifetime turns "just about making ends meet" into "retire 4 years early".