Do you exercise? I know all about lack of motivation. The last month or so though I've started using my cross trainer again, mainly to lose some weight and get a bit fitter but also it does make you feel better about yourself for quite awhile after you stop. Also if you do it regularly you kind of feel guilty if you don't do it. Not that anybody else cares of course. Use it in front of the TV if you can.
I've stopped a few voluntary jobs for various reasons and yeah you can get the impression you're not really valued. I should have gone today but I'm not really needed and I've decided to use my time for things 'I' want to do. It's OK to say 'screw other people' sometimes.