My key to keeping up the habit is to not miss a workout unless I absolutely have to. When I was pregnant and was told to take it really easy I would simply walk on the treadmill just to keep that habit up even if I wasn't building a ton of muscle or burning huge amounts of calories. I considered it almost a place holder for after I had the baby. I wouldn't have to reform that habit.
2) How I feel physically and mentally: This is mainly why I love power yoga. It's one of the only times I'm not thinking about the meeting I have next Tuesday or what to make for dinner, I'm just "being". Probably because I'm so focused on the "energy" (as my yoga teacher calls it) in that left leg we've been lunging on for however many minutes. Afterwards I feel relaxed and wonderful.
3) Who am I kidding....How I look: Who doesn't like to look toned and, not just fit into their pants, but look damn good doing it? I think enough said on this one.
4) Change things up: When I get really bored with what I'm doing I try something new. I've done Body Pump, Aerobics, Bosu, Yoga, Running, Swimming, Walking, Weights, Cardio equipment, Pilates, Yogalates, Gymnastics, Ice Skating, Roller Skating, Volleyball and just anything that keeps me active in general.
What keeps you motivated?