You can use personal inertia to make it easier to break your habit.
Anyone who is a fan of Bill Nye The Science Guy’s old TV show or is familiar with Sir Isaac Newton’s law of motion are already familiar with the fact that inertia is a property of matter and an object that is in motion stays in motion while an object at rest will stay at rest, unless they are acted upon by an outside force. The same is true when it comes to working out. Someone who is not used to exercising every day will not go out of their way to get themselves moving without anything motivating them to do so, and in contrast, people who are typically active are more likely to keep going with their exercise unless an injury or illness kicks them down, and then it becomes a bit harder for them to put themselves back into the saddle without forcing themselves to do so.
In the end, this can be worked to your advantage. Sure, you can use it as an excuse to go back to being sedentary, but you can also use it to push yourself to go harder. Just start out slow and watch yourself build momentum as you go. Start with a five-minute walk and then watch yourself as you get yourself moved up to a 30-minute run. Keeping track of your progress is always a good motivator to keep you going.