I think about living a lot- what I like, don't like and want to change. Part of my thinking about living includes fitness and what it takes to be active each day and make healthy choices. Spoiler- there doesn't seem to be an easy solution.
However, I do think the solution is simpler than we think. Yes, if you burn more calories than you take in you will see changes in your body, but that doesn't mean they will be the changes you want to see or be sustainable.
I'm talking about a simple solution that includes the flexibility to adapt to each day's demands so overall you can put "made healthy choices" in your win column.
When I teach Pilates classes I really try to emphasize in my cues that each person's body is different and that your body is different today than it was yesterday or will be tomorrow. I see people get frustrated that a particular move doesn't go as well as they think it should, and it kind of breaks my heart, seriously.
I think to myself that they made the healthy choice to get out to class with a certified instructor to give themselves a treat--a truly satisfying hour long work out to move, breath and feel their body. That is enough! It's that simple- make healthy choices throughout your day.
Coming to class and being aware of your body will allow you to compare that in future classes and start to draw associations---maybe that if you make more healthy choices before class (like getting enough sleep) you have a more enjoyable class. Healthy choices compound on each other- make one and it feeds the next. How many times have you worked out and then chosen a healthy snack afterward or lost your craving for an unhealthy one?
Building fitness and activity into your life so it becomes a lifestyle might not be easy, but it is simple. Make healthy choices. Make these healthy choices throughout your day at each decision point (which will become easier as they become your habit). It will fuel you. You will start seeing and feeling the connections. You will be able to go easy on yourself once you accept that you already made the healthy choice- anything extra is just the cherry on top.