Computers work for people, not the other way around. If it is easier for you to write and maintain 500 lines then the 1-line wonder is counterproductive. The difficult part is the maintenance. Understanding what you wrote a few weeks ago can be surprisingly difficult.
To make a big system work, you just apply the same principles you just learned. Keep everything in small modules that have defined functions. Just moving the mouse pointer on the screen is a difficult program to write but once it's done, everyone can use that module.