I think it might sound harsh to say, "Motivation is crap and it isn't going to get you anywhere." And it is harsh, but it is also true.
Motivation is great every once in a while. Motivation can push you to have an AWESOME workout! Or to achieve a short term goal, sure.
But there is something more that you will need to get through the really difficult places. The places where you yourself are sick of reading the motivating messages, or listening to the same techno song that used to get you pumped (Haha, referencing myself here). And that something more is a DECISION.
You have to make the choice, that every day you are going to try your best to be a healthier you. Another word for it is commitment, but to me commitment sounds very long term, and I am not a long term thinker. Commitment is too 'big' of a word for me. I need a smaller word. I can deal with making a DECISION. On days when decision is too long of a word I use the word CHOICE. And for the hardest days I use the word TRY.
Might sound simple, but it really isn't. You have to have an honest conversation with yourself and agree with youself that you are going to try your best today. Have this conversation every day.
Coming to this forum is a great way to do that. I login in the morning and report in on one of the challenge threads. That serves as me actually thinking through what it is going to take today to do what I need to do. I type it up. I post it. And I make the choice to try my best to achieve it.
Again, I wouldn't necessarily throw motivation out the window. You just don't want it to be the only thing standing between you and a brownie, haha!
Keep it up, you will get there. One day, one decision, one choice at a time!