Playing in a band did it for me. Not my first band, which was a pop punk band. Not my second band, which was like a melodic hardcore band. But, my 3rd band. Which is the cover band I'm currently in and have been in for 9 years now. Having to play just about genre of music and having to learn all the different styles and techniques of bass playing really made me grow as a player. I would still be pretty narrow skilled hadn't I joined my current band. But, I still have a LOT to learn.