Great thread. Inspirational in itself.
For me, the 'secret', and it is not a secret at all, is to study things properly and not to dip in and out without properly dealing with the thing you have chosen to look at. I have two example. On double bass, I got a bow when I got a double bass and have never 'studied' it until fairly recently when I picked up the bow and the Neil Tarlton book. I spent a few days.weeks working on the bow for a few minutes a day (20?) and, before I knew it, I was actually playing the thing. Same with double thumbing. I am not a slap fan but, like many bass players, I feel the need to stay on top of new things. I tried double thumbing a few years ago and didn't make much of it and I only return to it for a few moments every now andthen but, the other day, I started playing something and it was there. My incremental input had borne fruit. I use reading as a means of generating practive pieces. BAch Cello Suites are a rich vein for practice and inspiration. Transcriptions of solos of any kind. Even other solo transcriptions to bass; they are often transcribed in a different key to bass but you can still practice them in the wrong key and learn (I read treble clef also so this is easier for me). Try looking for new players, new genres etc.
Personally, and I mean this, there is nothing more inspirational that a straight quarter note walking bass line. If all else fails, I just walk a blues with NO accents, just straight quarter notes. Lush!!!