My car died today. Why does it always wait till you get 20 miles from the house?

I pulled over to make a call and shut the engine off. After a few minutes of unsuccessful attempts to reach my girl friend I got fed up and said fuck it and tried to start the car. Click click..Oh fuck, this happened to me before... the battery. So I opened the hood and looked maybe corrosion on the terminals, nah..they seemed pretty clean. Finally got someone to jump me and the car went woo woo woo but wouldn't turn over. Oh shit now what, well maybe the car that tried to jump me didn't have enough juice, so I asked another guy with a big pick up truck and it turned right over.
So I thanked the guy and sat back in the car and reved the engine because it sounded like it may stall and damn if it didn't. Oh shit now what, so I take one last look at the cables ..maybe they are loose. I had lost all hope of getting out of there at that point. The ground cable was a little loose and I twisted it down and woooom she started back up.
Every stop light on the way home was an ordeal, would she stall again. I got home a bit stressed out but with out further incident. Fuck it, I'll look at it in the morning.