I use to feel the same way wondering if I would ever master Blender then I got to thinking about it…LOL yes, bad bad thing of me to do! Unless you work in an industry where you are using Blender all the time, even then I am not sure it is even possible to master Blender because it is so packed with varying parts. It’s a good goal but are so many new things being added all the time it is a continuing learning process.
Oh, I think you can master parts of Blender’s creative process just not all of it. You can learn it but unless you use it all the time, it’s easy to forget part of it. Blender encompasses so many creative bits like texturing, modeling, rigging, animation, various map creation, uv mapping, nodes, etc. the list goes on and on. Unless you are really enamored with all the parts of Blender, I think most of us tend to stick with those parts of the program we enjoy. For me, I like modeling but really enjoy everything related to texturing though I am not really interested in animations or rigging. I tend to stick with the parts I like creating and limp along with those I don’t really care for.
Don’t make yourself crazy by worrying over mastering Blender. Master those thing you enjoy and keep adding to your knowledge!