Instead of skipping a routine completely if I have a bad day or just a hard time motivating myself, I scale it down and do SOMEthing! Instead of going for a run, I go for a walk, instead of doing a full 30 minute routine, I do 20, or 10. That way I keep up the habit and often, once I get started, the motivation to turn my walk into a run magically appears! 🙂
Put it on a to do list and mark it off after you have finished. Listen to music with a fast beat and the music will help you get focused on the music.