Yes I worry about it, but not obsessively. I did just quit the main band that I had been playing with for 10 years. The bl started doing some of his many solo and duo gigs with a bassist new to town. This bassist is very good, actually world-renowned and will some day most probably be famous, so although I'm a good bassist, this guy really is appreciably better. Like "jammed with Victor Wooten" better. Anyway all was ok until I went on vacation and the bl put this guy into some actual band gigs. First just a trio with the drummer, then a 4-piece. Bl did send an email that I was the bassist for the 5 piece, as hollow a distinction as that is, so really it was a situation where I could not win. The next gig I played would be a let-down no matter what, and after 10 years I did't want to be in that position, so I quit. I think the genuine interest this world-class bassist had in the band's music was actually cool. It also highlighted stylistic and musical differences I'd always had with the bl. The only reason the bl didn't fire me is because he wanted me around when this other bassist finally lands a big- deal touring gig. I wasn't up for that. I play with 3 other bands beside this one, and none of those bands were interested at all in hearing this guy play, let alone replacing me, so all in all I think things worked out for the best. But yeah, there's always someone better than you, and he may end up sliding inadvertently into your gig.