A perfectionist is defined as follows:
a person who refuses to accept any standard short of perfection.
But I am looking for a noun which describes a person who refuses to move forward in
an activity or thought unless the present one is sorted out. Kind of like having a mental block to move ahead, but by choice.
Best Answer
It's not listed in the major dictionaries, but Wiktionary mentions completionist:
I wouldn't count on your audience knowing exactly what it means, so you might have to explain it first, but you probably wouldn't get any closer with a single word.