I've learned if I skip a day, I end up skipping more than one because I reason with myself that my week is already screwed by skipping a day. I have to stick to a rigorous schedule. Monday-Friday, Saturday off, Sunday something outside like hiking up a mountain or something mind stimulating. If I'm up to it, I may so the gym Saturday too, but ALWAYS Monday through Friday.
I find that if I skip all days, I never feel guilty, because I'm being consistent. And that, is how I stay awesome.