Many times we make resolutions at the beginning of each year to get fit. Gyms pay big money to advertise things like, "A new year, a new you." Those ads pay off for them because people buy memberships; even if they don't use them. Why wouldn't you want to look better and of course be healthier?
You don't feel motivated to exercise because willpower isn't effective. Many times we bully ourselves to do something that we only want to do on a surface level. In other words, your deeper mind knows you don't really want to make that kind of drastic change to your comfortable lifestyle and it knows exactly how to keep you in your perceived rut. This rut is really your comfort zone and sorry to say it, but willpower is not even a tiny bit of enough to make long term changes.
Willpower is just enough to get you to join the gym and go a handful of times (usually in January) and then slowly you slide right back into your happy comfort zone (even though not so comfortable to you). The real reason we don't commit is always something deeper (inside of you). Your ego is brilliant at making up a fantabulous reason (always very convincing not only to you but to everyone you share your reason with) of why you can't, shouldn't, or won't exercise.
Not only do we feel like crap because we didn't get in our workout, but also feel like we sold ourselves out too. Resistance to forming new health/fitness patterns will show up. When the excuses start coming up, we know we have faced resistance. This is a good thing because now we can work with it by seeing exactly where we stop ourselves.
If we can begin to watch the excuses we use day in and day out, not judge, but just watch. Then we can start seeing how clever we are and how this mind game is your ego keeping you in the comfort zone. Redirecting the energy of your resistance is possible. Having a coach is one of the most effective ways to gently navigate the ego's resistance to a new health/fitness practice.