It'll come down to working up things into habits. No need to start out running a 5k every day. You can easily start by taking small steps or short walks, and when you're consistently going out and
doing, then you can build up. Same thing with DVDs or other types of workouts. You may not be able to do every single move, but you can keep time and walk in place, or tap your feet or do -something-.
I promise you it is far more important at the beginning to do
anything, rather than push yourself too hard and give up after two weeks.
You can definitely make sustainable changes! Reach out for as much support as you need on the boards. We're all here to give a little nudge to each other.