I started my game a couple months ago and I came across several problems too. Lack of motivation was one of them, which comes with procrastination resulting in less developing time.
So I'll share the thoughts of someone who isn't a successful developer (yet XD)
I'm developing a game because I love games, it's what I want to be my full-time job. For the first time in my life, I have what I can call a dream and my game is part of it.
Keep in mind why you started developing games. Remember the details.
When I feel demotivated usually It's because I forgot about that.
Now how to actually do it:
-The rule of thumb is routine! Work on your game every day (except Sunday). You don't need a full 8hr work every day or something like it. Give yourself a meta, start with 30min or 1hr a day and stay with it for a month or even more. If you do more, great, but never less than that.
-Start a post here!
Interact with the community is great. Believe me, it's great seeing people writing something about your work.
Don't be shy, almost everyone here is a beginner too.
-At GM use the comment tool so you won't feel lost when revising your code (drag and drop have something like it?). Also, have a notepad/wordpad or something where you write the logic you use with your game.
-GM already save your project files in a folder, so are you talking about things you didn't add yet?
Save all files related with your game at a single folder. References images, audios, ideas, etc.. So you don't need looking all over your pc to find that reference, that file etc...
- If the game you're working isn't too big already, start again can be a good idea since you can have a fresh start.
*You can work on your game at your rest day(Sunday?), if you want to and it feels like fun, but don't push yourself if you don't want. Everyone needs a rest day.
*Sleep early! (I still don't haha) The days I feel worse is when I sleep late (3 am at weekends). The days I felt "I'm on fire wooooÒoÓ" was when I was sleeping early for a couple days. At least it is how things are with me.
It doesn't matter if I sleep more than 8hrs a day, if I sleep late I'll feel all lazy and tired. There is some magic behind it @.@(circadian rhythm or something like it)
Or maybe I'm just a morning person =p