Tam links to a story about an Indiana Police chief that had his firearm discharge when a drawstring lock from his garment got lodged in the trigger guard of his Glock when he holstered it. She goes over all the other poor gun handling witnessed in the video. Safety is a habit.
Full disclosure, I used to wear a pullover as a cover garment when carrying that had a drawstring with lock. I had an entanglement of this sort happen to me once, but because I followed #6 of Tam’s lessons learned (don’t force the gun into the holster if something feels wrong), I didn’t have to shoot myself to learn #7 (that strings and triggers don’t mix). I’m also pretty religious about not unholstering the gun at all unless there’s a need to, and my holster is such I can remove it without unholstering the gun.