In fairness, Arm has usually traded at a price which is difficult to justify. As we found with the former high-flying SuperGroup; a stumble in operating performance can result in a massacre of the shares.
I have never been a holder of ARM, although I came close after the 2000-2003 tech crash and again after the 2007-9 crash.
Knowing when an asset is overvalued is easy in hindsight, but difficult in the heat of the moment at the time it peaks. The popular sentiment at the time can have a tremendous influence on our thought processes.
I usually have to override my emotions to make buys and sells because I am often going against current trends. When I took profits on silver in April 2011 (and again in September, along with some gold) I felt physically sick at selling a winner which everyone said was going to rise even more; fearing that I'd miss out as it went ever-higher and regret it for a lifetime.
As it turned out, logic actually kicked-in and now my silver and gold sale timing last looks to have been immaculate. I still hold some and actually I think it is close to the bottom of ts correction, but that's going a bit too far off topic.