Here is one objection and my response as to why some struggle with the emphasis on declarations:
I tried it, and it felt fake to me.
Some have attempted to make declarations in the past, and it just did not feel right, and therefore they quit. As we consider this, there are two things to consider: First, it is important to realize that many beneficial habits are not exciting in the beginning (e.g. exercise, nutrition, etc.). It takes time to get over the initial discomfort. Secondly, because declarations are so powerful in demolishing negative strongholds in our minds, we should not be surprised at the resistance that these long enduring belief systems put up. They just don't want to go. Even so, as you persevere in declaring truth, the confirming feelings will come.