I have felt the same, man. Many, many, times. I have actively practiced for over almost 15 years and I still don’t get the manifestations everyone else does. I used to feel like a failure as well, like magick just wouldn’t work for me.
Here is my old thread, from back in 04, just to show that you are not alone in what you are feeling:
A former member here, Arcane, channeled Belial for me, and what he said really struck home, and may be of relevance to you. With a bit of paraphrasing, He told me to, “stop comparing yourself to others. Spirit moves in its own time. It cannot be forced, and will open when it is ready.”
I took a break from magick but I could never really let it go. I have followed Belial’s advice and have let things unfold as Spirit dictates, and now I feel like I am finally, truly, advancing.