<human>: I have about seven hobbies that I cycle through every few weeks. I'll see something that inspires me to frantically focus on one, do it consistently for a week or two, then move on to the next one as I get bored and frustrated. My focus had been to get GOOD at the thing I was doing, and as a result of my constant switching, I'm just proficient at most of them. I know to keep myself motivated, I need to focus on enjoying them, which I try to as well, but my focus wavers. 
I really love all of these hobbies, but I feel like 7-ish (and counting, I'm interested in almost everything; surfing to painting to writing to knitting, everything sounds fun) is too many to really focus my attention a sufficient amount to any. 
Right now, here's my list:

* skateboarding/longboarding
* reading
* baking/cooking
* martial arts
* drawing
* snowboarding
* playing bass

I love all of them, but I feel like I can't continue attempting to do all of them without becoming stuck in a quagmire of mediocrity. How can I narrow this list down?/ Any advice for a guy like me?
thanks!

Condense the text into a few key points
<bot>: I have too many hobbies to juggle and I can't divide my time between them, and as a result I cycle through them every few days/weeks, never becoming more than proficient at them. help?