One of the best tips I've ever heard/used is to schedule your workouts like appointments. And for the most part, I can stick with that when my routine is going my way. Except life doesn't always go the way ya want, am I right? If I wake up late, feel like reading a book instead of leaving the house, or lacing up my sneakers seems more improbable than hiking up Mt. Kilimanjaro, I tend to turn to YouTube for some pretty great, 30-minute-or-less workout videos.  Below I've grabbed five of my favorites, from HIIT to Yoga, so you can fit a sweat session into even your busiest of days...