A few years ago during the Sturgis rally, my riding friend Ken and I witnessed a number of separate accidents resulting in 6 deaths and numerous serious injuries. We were never even remotely close to being involved, but in a couple of instances if we were less experienced riders, we certainly could have been. We went back to the rally a couple more times after that experience (during the rally week), but after 15 years of attending the rally, it was no longer fun. I think we both began watching other riders so much it took our fun out of riding. We've gone back a few times since then, but always the week before or the week after the actual rally week - and only for a few days.
For many years, I would ride in local "poker rides" or "fundraiser rides". Over time, I gradually became uncomfortable riding in large groups of people I don't know. Especially rides that involved most of the participants stopping in bars numerous times. I live an hour and half from Milwaukee, but didn't go to the 110th because I don't like the idea of riding around Milwaukee in large groups of strangers. Not because of me, but because I've seen too many things happen in groups, and I don't like the riding habits of many riders. I'm sure many others feel perfectly comfortable riding in large groups of strangers, but I don't (anymore), so I don't do it.
I still enjoy riding - a lot. But the only groups I ride with are friends whose habits I know, who know my habits, and whose instincts I trust. Our riding vacations are rarely on interstate highways, and are generally in the western and north western mountain states (beautiful scenery and very little road traffic).
My suggestion to all riders is to always ride within yourself, use your experience and don't do anything that doesn't feel safe, don't feel pressured by riding partners to ride outside your personal boundaries, and have fun. When it stops being fun or stops feeling safe, then give it up.