I'll start by stating the obvious. Whatever physical activity you choose, you must enjoy it to make it sustainable. That may take some trial and error. Or may be a single or a variety of activities. For instance, I never thought I would enjoy running - ever! But that's my goto. So don't be afraid to try different things. And, like anything else, you won't enjoy it every single day/session. Be patient with it - sometimes fighting through those days gives you the greatest sense of accomplishment. Start small and allow your body to adapt gradually to avoid injury.
Most importantly, don't view it as an activity that you must do. View it as part of your routine. After a while, it simply becomes part of your lifestyle. You'll feel better, look better, live longer, and the quality of just about everything in your life will change as a result. You'll likely also meet like-minded enthusiasts who share a passion for the activity (like this community). Good luck!