The drummer might inspire me to play something. The musicians listen to one another and make spontaneous decisions. The possibilities are endless. The joy of performing is the group sound. I can't play whatever I want whenever I want.
Jazz is democratic music and everybody gets to solo but only within the context of the whole.
The group is what is the most important thing. Sometimes the best thing for me to do is not to play. And to respect another's musical space. When I do solo, I still have to pay attention to what the rhythm behind me is. I can't ignore it.