I agree that it's nearly impossible to hold onto shares when emotions are in control. This was a problem I had for many years and my results suffered significantly. Happily I've been able to keep them out of my decisions most of the time and that's due to following rules.
Differently than you, I've found the gains mentioned attainable in many of the ideas I've followed if the rules are followed. The suggestion is to sell some shares but not the entire position at certain times. The remainder of the position if held attains those levels.
There are times when I've bought back shares at price levels where shares could have been bought back at lower levels and other times at higher levels. There's no rule that says don't buy back at higher levels that I've ever read and there have been examples where re-buys at higher levels where identified.
From my perspective the more important question is how can I optimize my portfolio gain. When considering repurchases, the question is am I better buying back or better putting the funds into another idea?
Even when the originally purchased stock resumes it rally and goes much higher, there are often times the total gain for a portfolio position is much greater if those funds are allocated to new positions in other ideas.
I've got my own thoughts on this as to which way to go. Two of the more important ones involve where the respective stocks are positioned from a theme and market cycle perspective.