It is true that focusing on one thing (mastering one skillset or aspect of your work) makes you an expert at that. In some jobs you need to do that, but even then, it is always good to have a broad range of knowledge in the field, so you know your basics well.

Anyways, I have many interests in the creative field and it is hard for me to focus on only one thing. I have many projects in mind that I would like to complete, that require me to learn a new skill or practice the ones I've already learned. Writing down the plan of actions and listing the time frame for the project helps me with that. Also, I realized that I can't do/make everything, and that I need to let go of some ideas, or at least keep them in my "ideas vault" for now, so I can concentrate on the stuff I'm currently working on.