GET A GOOD MENTOR/TEACHER/FRIEND/MUSICIAN to teach you or study alongside you. Learning jazz was never meant to be you and a theory book, no matter how comprehensive it is. Live the jazz life - listen to as much live jazz as you can, transcribe bass lines from recordings of jazz bass greats (you may not want to do Jaco just yet), learn your scales (much easier said than done, esp when you move on to the minor scale and its modes), always practice with a metronome, and again, get a good teacher.