I’m struggling a bit with motivation myself, and I found that it’s very important to clearly define why you want to stop and why you don’t , and make a cost-benefit analysis for changing and not changing. This is one of the exercises in the flight to freedom program, lesson 2. I would suggest that you check it out if you haven’t already.

It's very normal to have a powerful burst of motivation to start, and for that to taper off, leaving you uninspired and unmotivated. It's a part of the fight.
There are two aspects of motivation - inspiration/emotion and intellectual understanding. The fire, the inspiration, by definition doesn't last. But it's a very powerful force and a crucial tool in this battle. It got you fired up and through the first part of this journey. As Oived Elokim said, aside from the inspiration, a person needs to have a clear intellectual understanding of why he wants to break free, and even after we know it, reviewing it, clarifying it until it's deeply embedded takes time and effort. The powerful emotions and inspiration can also be reignited at times, but it's the understanding and knowledge that needs to be constant and will carry you through the valleys when inspiration and motivation are low. I'm sure you are aware of the reasons you want to stop, but it still requires a lot of review and focus. 
Personally, I'm going through a bit of a lull in inspiration myself so I'm talking to myself as much as you.
Keep up the great work!

Hi Youngertwin, 

Do you have a sense of what's leading you to your falls? In my experience, feelings of stress or despair about my life in general can lead me down that path. I've noticed that urges often don't come from a physical desire per se, but are instead an expression of pain on some level and a desire to walk away from who we are. Who you are is literally a piece of G-d. You're a holy and important part of Hashem's world. I heard a great saying once: "once you were born, the world decided it couldn't live without you." Don't believe the lie that you aren't essential, or that you've somehow lost the ability to succeed in your life. Only you can accomplish what it is you have to do here. I haven't met you, but I fully believe you are capable of actualizing your potential in this world. Don't be scared to take up the mantle of who you truly are, because in truth you are way way above all the nonsense that's out there online. Don't let that silly stuff pull you away from who you are and what your mission here is. And whatever the emotional/psychological challenges you have are, you will without a doubt overcome them

It says in gemara that when all else fails to help you not sin, remember the day of death when you will be ודומו סלה silent forever.