There are many attributes of great musicianship. Knowledge of theory, technical skill, feel, or intuition to name a few. However, the attribute that I value the most from my musician friends has been kindness.
I share this openly, because I think every musician has had to deal with this at some point. For me, the greatest obstacle to my performance, in general, is fluctuating self confidence. Performance anxiety is never truly overcome. It takes considerable discipline of will to get my prefrontal cortex out of the way, so I become less aware of myself, and can put energy into a song. I can specifically remember times when feeling that in my mind I was seriously sucking. One such time a musician friend told me "I rocked". Another such time I was told, "you have an incredible attack". These small statements made all the difference. Other times when I truly sucked, patience, and kindness got me beyond where I was, motivating me to continue.
While I have come across a few arrogant musicians, for the most part, kindness, and patience is the overriding personality. We all started somewhere, and we all struggle with the same things to some extent. I wouldn't be half the musician, or person I am were it not for the reservoirs of kindness that have been opened to me. I only hope I can even begin to pay this forward in some way.