I went through this for over a decade! I'd lose weight, but looking and feeling good was not enough to keep my diet going or my exercising. My "need" for sweets and my natural disposition to sit rather than get moving always won. For me diet and exercise felt like a job and I too felt like 'how long can I really keep doing this?'
First I attempted to solve to exercise issue. For me I'd alway been an on again off again gym goer, because really I don't like the gym. I'm not a people person and I found especially more crowded times to be annoying. I wanted working out to be a pleasurable thing I liked forward to, not a chore. About a year ago, I began using a treadmill at home, which helped a little. When I took my running outdoors, I finally, first time in my life LIKED working out. It was peaceful, alone time I'd wanted. What I'm trying to say is if the gym isn't working for you, ask yourself what you would like you workout to be like, maybe swimming is better or biking? I don't even think of running as working out. I love running. I can do it forever. 90% of the time I want to go running, and I do push myself the other 10%.
I found the diet part to be harder. Eventually I'd always go back to over eating or eating sweets. Lots of sweets. Allowing a little treat here and there turned into a lot of treats. Slowly I changed my general way of eating to mostly whole foods so most of my diet is healthy but I still couldn't tackle the sweets. For me, I recently stopped eating sugar. And for the first time my appetite is under control. That may or may not work for you. Some people give up white flour, some do well with low carb, some may go vegetarian or vegan. Play around with our diet until ou find away of eating that controls your hunger if it's cravings you are dealing with. If you are just feeling restricted them try not to cut out all 'bad' foods but allow them in moderation. This works for some people as well.
You have to find a new eating plan and exercise that you can do the rest of your life. And treat them separately. If I decided to pig out for the next week,I'd still run. Likewise if I didn't run all week, I'd still eat the way I do. And give it time. It took me almost a year to really have running a part of my life. And dietary changes can take a while to feel like they are normal for you rather than a diet.
This is not a plug for running, but if you haven't tried it, ou should! It's a little addicting actually!
