How do you stop feeling lazy

I work a lot, but it seems to come in waves.  Right now, I am in a down crest.  I have a few things to do, but not as many as normal and I just don’t have motivation to do what needs to get done.  As a result, I just feel lazy.  It’s not as though my I don’t do anything, I just can’t seem to get over the hump to being productive.  Part of me wants to know how to fix that during down cycles, but most of me wants to know how to remove this sense of guilt of being lazy.  I truly believe I do enough to be a good employee and I shouldn’t feel guilty for these short periods of lower productivity, but alas I do.  I guess being lazy, feeling like a lazy person, and working through it is something I need to work on...if I find the energy.