I can definitely sympathize with the lack of self-discipline as well. It's difficult to discipline yourself when the animus to do so is faltering.

Besides that, I've found myself growing ever more sensitive to lighting, natural or otherwise. The 'fluorescent sunshine' from the overhead fixtures typical to most office environments is a definite demotivator. Likewise, I usually remove those ubiquitous, vinyl miniblinds from any new apartment and replace them with Chinese-style roll-up blinds with opaque fabric to allow in natural light.