Bruce, when I started learning tenor banjo, I wanted to play it more than any other instrument which I guess helped a lot. I also used to play along with recordings which helped.I let my music slip quite a lot over the last 4 years but I have recently moved and found a great session. This to me, provides the biggest incentive of all. I love playing with others, so even though I'm not to fond of my own instrument on its own, I'm back to just wanting to play...
To follow on from Rick's suggestion, it would also be possible to set up tracks on your computer using Midi and there may even be some ready made ones that you could find.
Jon