I may be in the same boat. If you are basically content with your level of play, and don't honestly think you'll ever go up a speed, there's not much motivation.
Now, whether you ACTUALLY can't go up a speed, is a different story. But if you think you can't, that's enough to make practice feel boring and pointless.
The only practice I get these days is with someone who hasn't gotten there yet... he enjoys practice-type games, we do a safety game where all you do is play safes and then the other guys kicks at them. This is as close to practice as I get and I honestly enjoy it and can do it for hours. So basically, I have to steal someone else's desire in order to practice. If I had a table in my basement I don't think I could accomplish anything alone.
I guess that's my advice... find someone who wants to improve and practice, and find some entertaining way to practice together that doesn't involve simply playing racks of 8b, 9b, etc.
th only people i play with are c players at best, it gets really old to win all the time, so i just work on harder shot/ leaves when playing lesser competition. playing down to there level is not good for your game if you get in the habit of it. also teaching them what i know keeps things fresh so they can improve and i feel like im helping them out with there progress. justa a lil rant, ahaha.