I can certainly lose my momentum on something, which means it gets set aside and something else gets started. Sigh! That's why I have so many works in progress!!!
Sometimes looking at a picture of the finished object helps, but I still have to switch to another quicker project sometimes. With spring coming soon, I'll be doing more gardening, fishing, kayaking, and other outdoor activities. When that happens knitting is not high on the list of things to do. Then about the middle of broiling summer I pick things back up again.
So, yah, hitting a wall is normal; you just have to figure out the best way to deal with it!