Motivation is fleeting.
But when you get it, in my opinion, milk it for all its worth. If you want motivation, go to the library and check out the health books and educate yourself, learn healthy recipies, check out before and after pictures of people here, prepare a mix of workout music to use. Hopefully the motivation can trigger you into a good habit at the very least, but ultimately, you need to set up your life so that when the motivation does go out the window (and it's only a matter of WHEN it does) your world is arranged so it will pull you through. For example. If you clear your cupboard of tempting foods, even if you WANT to indulge in a huge bowl of icecream, you can't because you've set it up so its not in reach. A gym membership is another one that helps me. Even if I don't feel like exercising, I've paid all that money to go. Laying out my exercise clothes helps too.
What I did before I started my weightloss journey was write a pros and cons list on being fat. Needless to say, the cons went for 4 pages and I struggled to come up with 6 pros. I give it a read over when I'm discouraged and it helps me to keep on track. You could try writing a list like that. It's pretty confronting and hopefully will help you keep going.
Nice to meet everybody btw