The bass guitar is as much a rhythmical instrument as it is a harmonic instrument. This is why we must view the study of rhythm itself as being of equal importance as the study of harmony (scales, chord tones etc).
Unfortunately this is often forgotten, and students spend 99% of their time working on harmonic exercises such as scales, arpeggios and such.
I'm sure you can relate to this feeling… 'If I can learn just one more scale!'… 'If I could only play that bit faster!'… this is what I call 'chasing your tail'. You'll always want to play faster, you'll always want one more scale!
It is important to understand that rhythm and harmony are the pillars of all music. Therefore, when you study them separately, and then bring them together, your bass playing will sound infinitely more mature and… BAD ASS! ;)
Now grab your bass and get in the shed!