I get what you are saying, I am one of those that tends towards depression and sometimes I wonder whether life is worth living. I finally realized that it was up to me to find a purpose, I had to find a reason to get up in the morning. I believe we all have a gift to bring to the world, and it is up to us to figure out what that is and then do it. You are a musician, maybe that is your gift. Maybe it's playing the music others want to hear and and maybe your gift is your own music, that's for you to find out. You can only know by getting out there and doing it whole heartedly and without fear. You may never be famous, but that doesn't mean your efforts are in vain because of you are doing what you love and what fulfils you then you are a success.
I have struggled with this myself, I wonder why I feel this need and the way forward is not always certain, but I find I can only be my best self when creativity is part of my life, so I make it happen.
So go play some guitar already!
Lisa๐น