http://blog.jessitron.com/2017/06/the-most-productive-circumstances-for.html?m=1
I’ve see too many good devs beating themselves up for not being that 10x developer.
tl;dr 10x productivity requires specific environmental conditions. It can be replicated, but only with small projects. Don’t expect it all the time. Don’t beat yourself up for not getting to that level – especially on somebody else’s codebase.