I think a lot of the struggle that many people face with the feeling part of the manifesting process is still being stuck in your current physical reality and not being able to get out of seeing what your body is "now". You decide what you want and put it out into the universe and you visualize what you want and then you try to feel as if you already have it but then your circumstances (people, places, mirrors, etc,) make you feel as though you're still not what you want right "now".
But an interesting way to look at it is that there are an infinite amount of parallel existences and earths. All with an infinite amount of possibilities. An earth where you are exactly how you appear right now, another where you are exactly the way that you want to be, and an infinite amount of others.
You don't have to worry about not feeling the way you want to be because in your parallel reality you are EXACTLY how you want to be and with knowing that you can release any doubts or worries or resistance because it is.
Just a nice perspective I like to take when going through my day.
Here's a video that may help with understanding the concept of realities and how to put that understanding to good use.
Hope you all have a wonderful day!