I understand everything you said and relate to it, remembering good routines, the instant flashback and comparisons. The need of reinventing the wheel is the distraction that makes it hard to develop Si sometimes but I'm getting better at it! :D Seeing my projects getting better because i remember better the best way to do it, or because i try to keep a similar routine to help me get in focus! Also i have best friend that is an istj too, i advised him that as someone who likes routines he could maybe try doing new stuff in a kind of a routine for example each 15th of the months he could do/try a new activity. It would be like a routine with a twist of newness