One thing that really bothered me when first starting out with Squeak, was the requirement for modifying code in order add 'self halt' to work with the debugger.
I still find that to be bothersome. Intuitively it seems to me that breakpoints should have no way to modify code.

At the early stages, I wanted to add a few breakpoints so I could more easily follow along with what was happening and in no time at all, I would have lost where I had modified code to add the halts. I wanted to keep everything pristine so I could be absolutely sure I had done nothing to negatively affect Squeak's operation. I had a great uneasiness that I would mistakenly delete a line or add something incorrect somewhere never to be found again. The only solution was to quit without saving but that lost everything I had done in the Workspace and I didn't know enough yet to easily save and restore my work.  

It was great to be able to see and modify anything anywhere but along with that came the great fear I would mess things up. Even adding a method for learning purposes somewhere in the system was problematic since I did not know about or understand ChangeSets and could not easily remember where the change was done or ever find it again. I desperately wanted a way to clearly know, 'here's what I have done', and if I remove all that I have done, I in no way will have affected what came with the fresh image. 

It's still somewhat of a worry in fact, therefore I am encouraged by Keith's Installer which allows more easily starting over from fresh and getting back to my previous state of the image.

Ken G. Brown