Wow! This is a hard post for me to respond to, as it feels like I have an opportunity to talk to myself 16 years ago...
Not that long ago, I would have said, "Pick a diet and do it. Pick and exercise and do it." But I know that doesn't work.
Here is what has worked for me:

Find an exercise you LOVE. I hated all forms of exercise, so I decided to force myself to pick one and love it. I picked running. Don't get me wrong. I like it. I get a good calorie burn from it. I've ran a 10K and a Half with amazing times for my short history and weight. But I discovered Crossfit and actually LOVE it. Take a bit of time and try stuff. Even if it's scary. Find what you love, it will last and it won't seem like "work".

Don't make any short term changes. When I started out for this final weight loss journey, I made myself a promise. I would not do anything that I couldn't maintain for life. Now, this does NOT mean I will never change or modify things, but that I would actually THINK about my choices. Can I never eat gluten again? yes, because it makes me sick and in pain. Can I never eat chocolate again? no, because that would suck. So I made it a rule that if it is within my calorie count, I could have chocolate. If I start abusing it, rethink.

Count calories. Weigh yourself. Record your data! I started with the rough estimate of body weight x10. Recorded everything I ate. Recorded my exercise. Recorded my weight every day. Eventually, I figured out that if I exercise for 1 hour I can eat 1600-1700 calories a day and maintain/lose. If I don't exercise that day, I need to eat 1300-1500 to maintain/lose. I didn't think my body was that predictable, but it is. Learn your body and use it to your advantage!

Forgive yourself. For missing 1 day of exercise, for eating 100 too many calories. The more you beat yourself up, the harder it seems. Today is that day for me. My weight was up 0.8 lbs. Well guess what? I didn't count calories yesterday, I didn't exercise. I know my body. I can't beat myself up, because I KNEW my weight would be up. I have to say, "If you wanted to see a loss, you should have not had a lazy day yesterday." and move on. It has been the hardest part of my journey, but closing in on maintenance, I am realizing it is the most important part.
Good luck, and don't give up. 1 change at a time, 1 moment at a time.