Most replies here are missing the most important point:
How do you get motivated to become physically active? By
finding something you enjoy doing. That's the most important part of the process at first. If you only do something because it works but you hate it, you will end up stopping and go back to inertia.
Do you know whats the second most important part of that process?
Stick with it. That might sound contradictory with what I said, but it's not. Most likely, before you find the form of exercise(s) that's best for you, you'll probably end up going through a few different things and you won't enjoy them. There could be two reasons for that: 1) It's genuinely not something you enjoy 2) You're just not used to doing them. For example:
No one likes running, at first. I mean, it sucks. However, if you stick with it for more than a couple of runs, you'll find that like most people who give it a try, that you enjoy it. Something clicks in your brain and you go 'Holy shit. This is
fun.' Same goes with weight lifting, and many other activities/sports.
So if you want to get in shape, you can start something like
Couch to 5k. At first, it's gonna suck. The more you stick with it, however, the more you'll start enjoying it. At some point you'll be really looking forward to it. And then at some point you'll get annoyed by rest days because you really feel the urge to run. Then you'll ignore rest days, get an injury and get even more annoyed you can't run at all, but won't act like a retard in the future and learn to not run on rest days even if it sucks.
Replace running with basically any kind of physical activity. That's more or less the universal process everyone goes through. Which brings me to the third point:
Don't be a retard, rest days exist for a reason.
Once you've started getting active and you see real changes, or when it''s been a while and you're really comfortable, you will feel constantly tempted to do more and more and more and always push the envelop. Don't. Stick with programs, stick with rest days, this shit exists for a reason.
tl;dr:
1) Try many things until you find what you really love
2) Stick with everything you try for a while to make sure it's not just the beginner's curve you don't like
3) Resting and taking care of yourself is as important as training when you lead an active lifestyle