Lack of motivation

Technically today is an "off day" in terms of exercise, but I work crappy shifts this weekend (friday until 2am, back at work by 11am on saturday then 3-midnight on sunday) so I know It will be a miracle if I can force myself into the gym over the weekend...I NEED to go today. I absolutely 100% MUST go...so why can't I unwrap myself from my blanket and put my gym clothes on?