Motivation versus Discipline?
When it's cold outside it can be hard to stay motivated to exercise especially outdoors. No doubt you'd rather put on cosy layers and curl up by a fire.
Motivation, "a willingness to do something", is often a transient and therefore unreliable state of mind. Real success comes from discipline. When you have discipline in your life you can make small sacrifices in the present for a better life in the future. Discipline creates habits, habits make routines, and routines become who you are daily.
The key to creating discipline in your life is to make it sustainable. Consider aiming to go out for a walk every day for just 10 minutes, or create a list of 10 exercises and make yourself do at-least 3 of them 10 times each, i.e. Push-ups off the kitchen bench x5, sit to stand squats x 5, stand on one leg for 30seconds L and R. They don't have to be hard, or for long, but try to create a blend of core, upper and lower body, balance and range of movement based exercises.
Start small and remember from little things, big things grow.